My Kilo Motor

[850cc racer]

Hey guys so im going to have a crack at the kilo record over here in aus for 1250cc mono. its currently set with a boat the same as mine but with a 920cc on it at 83mph i think it is.

Im wanting to have a go at it but with a 814cc.

I have a hustler 75hp, Phil's mod 50 pistons and the matching rods, im going to use my straight in 5pedal front with the 1inch carbs on it.

what im needing to know is what should i do it it:confused:, it'll be fingerported, but im thinking it'll need to be spinning well into the 7's
i also know this motor will only be good for a kilo run not normal circuit racing..

my current motor does 75mph, its 814 fingerported with a single throat front, 2-1 gear ratio and 12x23 @6500rpm.

i have 2.4-1, 2-1, and like a 1.85-1 gearboxes for it and many props. 12x23 12x25 13x23 13x27 and so on.

all help is muchly appreciated!

850:)

[850cc racer]

Hey guys i had a pm from a member advising me that my boats only doing 60.7 by a formula from some website.. this is not a "slanging" reply or anything like that just wanted to let people know the speed is definitely true and not made up!! a website formula isnt real time situations.

help with the internals of this kilo motor is muchly appreciated.

thanks.

[88workcar]

If it is going to be a one time deal, put some serious compression on it and put it on racing fuel. I think that 1" carbs are rather small for that engine, but I definitly am not an expert on that engine. Good luck keep us posted.

[Powerabout]

I would have thought the tallest ratio and engine as high as you can get it.
( get a tow onto the plane..it that legal?)

Just a thought but..
6500 sounds a bit low when a sst60 should be doing 7 to 7500 ( according to the manual ) with shorter rods more cubes and 3 x 1 1/2 carbs and an average exhaust and you can go to town on your exhaust.

How much did you raise the porting to suit the long rods?
Have a play here and you can see how much retarded the port openings become when the rod gets longer
http://www.torqsoft.net/piston-position.html
Or if you have the head off a stock rod engine with same porting, check the timing and compare it

Anyone got a M31 port timing map?
Where's Fred when you need him?

Pitch x rpm
-----------
ratio x 1056

= theoretical mph

I think the rough part is always the prop pitch when most blades have progressive pitch and cup what do you actually use ? I think there is some trick with lipstick..you will need to ask Ron H

Small stuff....use ATF in the gearbox
make a sleeve up so you can remove reverse gear...
Use race fuel not Av gas ..Longer rod is more prone to detonate than a shorter
I have heard of people taking the wp impeller out if you run a LWP.....never tried that one.

[JohnsonM50]

Hey guys i had a pm from a member advising me that my boats only doing 60.7 by a formula from some website.. this is not a "slanging" reply or anything like that just wanted to let people know the speed is definitely true and not made up!! a website formula isnt real time situations.

help with the internals of this kilo motor is muchly appreciated.

thanks.
With the specs you gave, 1st post I find potential speed to be 70.79mph. Im not trying to cast doubt tho just to say there are variables on the boat beyond arithmetic while #s are cut & dry. The 1.85 :1 ratio with the 12 x 23 prop @ 6500Rs could potentially go 76.4. I dont know much about the powerhead except to say it will need to produce power at much more rpm. for that 83mph+ mark. At 2:1, 23P youll need a minimum of 7700 Rs to reach 83.8 & thats before subtracting slip/resistance that can vari from about 90% [very efficient] or less.
What I do to get these #s is Pitch times RPM divided by 12, times 60 divided by 5280, times Ratio. [.5 in this case]= Potential Speed. To get ratio I divide the low # of gear teeth by the high #. for instance Yamato 14/15s = .933:1 using .933 to multiply. Best of Luck with that run for the record. :cool:

[88workcar]

In the defence of 850, last evening I tested 2 22p props, at this time my engine will only turn up to 6900rpms. With one prop I ran 60.9mph and with the other I ran 69.9mph. And with my reg prop 26p cleaver at 6600 rpm I run 77mph.
I think that either his pitch or gearing is not a good number. Or even the tach may be off. 850, is your current speed GPS? The picture sure looks like 75mph.
And I agree go with the tall gear and prop to it.

[JohnsonM50]

In the defence of 850, last evening I tested 2 22p props, at this time my engine will only turn up to 6900rpms. With one prop I ran 60.9mph and with the other I ran 69.9mph. And with my reg prop 26p cleaver at 6600 rpm I run 77mph.
I think that either his pitch or gearing is not a good number. Or even the tach may be off. 850, is your current speed GPS? The picture sure looks like 75mph.
And I agree go with the tall gear and prop to it.
Im guessing that too, Most guys are using gps nowadays so one of values is off. The boat couldnt possibly trim better if its hangin where the pic shows it. This will be about prop every bit as much as motor or ratio. :cool:

[850cc racer]

Hey guys yeh it was with two different gps's that we have checked the speed of it.

im going to have a look at the torqsoft website for sure thanks for that one.

on the exhaust side of it.. cos ill run a tuner in the midsection ive been told i should dry that out so ill exit all water from the head?
also i should port match the exhaust?

does all this sound right? i understand i can block the water return in the sandwich plate..
how do i port match though?

thanks guys for all your replys

850

[Powerabout]

Here's the record
OUTBOARD MONO HULL CLASS SPEED RECORDS (Kilometres per Hour) AS AT 2 AUGUST 2009
1250cc
MONO HULL
STEVE'S JEM
S Medaris
131.58 KPH
Dargle NSW
8.8.93


http://www.ausapba.com.au/download_index.htm
download rule book
last few pages

Will they let the 49er into the 800cc class as the UIM used to do?

[850cc racer]

Hey Powerabout thats the one. seems i have to do 84mph which will be including the +2%

i started to play with the exhaust ports this afternoon and copied them from the 814cc thats already done.
im going to send it away tomorrow to have the fingerports put in it.
i have the mod 50 map Fred sent me some time ago so they'll be copied from that

anyone have any suggestions on what head, igntion, fuel, jets should be?

as i mentioned im going to use the straight in front with the 1inch carbs

thanks
850

[Powerabout]

A real good exhaust is were I would be looking
There are at least 3 different types on FF's thread.
If you look at them several follow the style like the original looper had.
Seems to be the go as used on the M31 as well.
I reckon you could make that yourself
Guessing but I would say the reason the looper went to the style of exhaust like a 70/75 has is to broaden the torque curve, not something you need on a kilo engine.
Those were the days of cross flow grunt and the loopers had less. Probably explains the low gear ratios as well.

PM philmyrna_shakesby he knows a thing or 2 about loopers

[850cc racer]

so ive been thinking about carbys and reeds.. heres some different options i have...

these single stage 6 over 6 carbon fibre looking reeds, they can either be put on the proper reed block or run on these "fabricated" blocks.

http://img190.imageshack.us/img190/3626/img3282a.jpg (http://img190.imageshack.us/i/img3282a.jpg/)

2 stage 5 over 5 plastic reeds, they are what was on my straight in front

http://img25.imageshack.us/img25/4279/img3284sw.jpg (http://img25.imageshack.us/i/img3284sw.jpg/)



the reed blocks arent sitting flat as there was bits of gasket here and there

does anyone have some pro's or cons on the reeds for me?

[850cc racer]

thanks for the reply too powerabout, i have been talking to Tim Krucz. :cool:

[plasterer timgarfield]

hey buddy forget it just get mark mctye to build it for you he,ll do it right and probably show you how to do it too all the best with it wheres the kilo run rosevears,franklin?

[850cc racer]

Hey mate, are you in Tas? yeh i have actually gone down a different track now..
bought brand new Mod 50 im thinking that will be the best i can get :cool::eek:

it'll be run in devonport late november.

850

[plasterer timgarfield]

nah buddy grew up down there livin on gold coast now

knew dereck pretty well when racing was still goin up here

im muckin around with one of your boats now makin it wider

and longer to take a v4 omc another work in progress a 5yr project

tim

[Powerabout]

Hey mate, are you in Tas? yeh i have actually gone down a different track now..
bought brand new Mod 50 im thinking that will be the best i can get :cool::eek:

it'll be run in devonport late november.

850

Wow where do you get a brand new MOD 50 from?

[850cc racer]

from the new mod50 store? :eek::cool::D

i have been lucky enough to find this..

[Powerabout]

Nice one
Can you do a port map before you assemble it???
Cheers

[850cc racer]

ahhh im not really good at stuff like that. im thinking the owner is though:rolleyes:. and cos its not mine for about a week i reckon ill mention to owner and see if they want to share...

this thing will make my mono scream..:eek::cool:

its going to be awesome.

850

[850cc racer]

exhaust

[Powerabout]

thats a nice bit
I think you will need the adapter to suit

[850cc racer]

......

[Powerabout]

Nice
Is that the plate for the race mid and twin pinion lower ya?
Are you going to use the twin pinion lower...
you might raise the record quite a bit!!!

[850cc racer]

Hey there. na no twin pinon lower.. rules there are some. thru hub exhaust. no quickfoot. however gearbox modifications are unlimited from what i read. Reverse? nope that wont be needed.. better get that outta there.

watch this space.

[Detroit Whitey]

if ya take it out it will never last hek might not make it down the corse

[850cc racer]

Take the gear out and machine a shaft to replace it with...

[Powerabout]

850
Where do I go to find the rules?
Thanks

[850cc racer]

its on its way:eek::eek:

seems iceland has real fast courier servies!:rolleyes:

[Fast Fred]

run the 1.85 to 1 foot (faster), you want the motor loose, top ring only be best, run the mod50 exhaust, biggest two banger carbs you can get on there (1" 5/16) i'm thinkin:eek::cool:

[Freddie Webb]

You don't take the gear out you take the teeth off and use it as a spacer. I have one in my v4 crossflow that I have run for years and Wilbur and Wayne Weeks did it in the 70s. It will work.

[850cc racer]

Fred you are still here!! hadnt seen you post in weeks.

well ill be running the 1.85, and yeh i understand about taking the teeth off..

ill be running the motor as i have been told to by the Master... and please dont think im not taking on your suggestions fred.. ill just do as ive been told...dont want any blow ups or that... na im gonna run the 1inch carbs..

ill have the package in 48hrs, aus customs havent been real nice to me, seems they just want to make things hard.. maybe cos it came from iceland?

who knows.
850.

[Powerabout]

850
what did you find in Iceland?

[850cc racer]

a mod 50?

[850cc racer]

The kilo is 16 days away!!.. how long before my mod 50 is ready to light up??

im thinking saturday :eek::cool:

she'll be all dressed and ready tomorrow night:D

gotta clean up my nitro 1.85-1 make her go through the water real nice.

paint or no paint on the lower???? she has a nose cone on her, the expoy style stuff (car bog) real nice one..

[Powerabout]

great stuff
dont forget the photos

[850cc racer]

thanks its come together real nice:cool:

[850cc racer]

Mod 50 is all together.:cool: could have ran it tomorrow but want to do a few more things. next saturday she'll be lit up :eek:

850

[1850guy]

hey 850 i like the look of your hull can you tell me a bit about it?
its just the sort of thing im lookin for.
who makes them and where?
what length, width, weight ect?

Cheers Mike

[850cc racer]

Hey mike where abouts are you from?

[1850guy]

Christchurch New Zealand

[1850guy]

Christchurch New Zealand

[850cc racer]

ahhh nice as.

well its a steve medaris hull.
weight not sure. i could do that though.
length is 14ft
perfect hull. rough water its a little light but she does 75mph with a single throat fingerported 49 triple omc.

really good feel and predictable. id like to buy the molds of them.

dont know of any for sale but could ask around.

cheers
850

p.s. ill try and get some footage next sunday when i take it out with the mod 50 on the back.

[1850guy]

sweet would love to see some footage,
take it steve dosent make them comercialy?
years ago when i was building bullets and tennessee's here we made a 14 foot tennessee by putting a stopper in the 17 footer mould, went great with a 920cc on, but the moulds are long time destroyed now.
would love to get a class about that size up for interest here, effectively f3 size motas but on mono's, pretty much wat you are running by the looks of it.

[Powerabout]

I'd love to get some as well but have had to go to Canada to get supply of some new Critchfields.

850 will you still be allowed to race that without any driver protection in OZ?

[850cc racer]

yeh wicked as well no he doesnt make them commercially. i know theres molds about. could even flop one off my boat? would that work correctly?
yeh i have ran it with an 814 and 920, the 920 wasnt tuned right but did get it on quite well, although alot of that being for the dual throat carbies.

these are the best to drive.

the cell rule is only for inboards.. basically anything being made over 6 litre has to have a cell i believe.

[850cc racer]

well the Mod50 is looking better and better each night. cant wait to hear it run!:eek::cool:

[88workcar]

I have always kept an eye on you, hope you blow the record away, put up some Vid for us.

[850cc racer]

Hey cheers. yeh ill see if i can get some footage when i take it out.. cowl on of course :cool:;)

[Powerabout]

Are you going to run race fuel?
What oil ratio does your guru suggest?
Best of luck

[850cc racer]

well the boat will be flying so not sure what fuel ill run :cool::rolleyes:
not sure on that one?

what do you think is good?

850

[Powerabout]

As with any OMC race motor they would say 4%, 25:1 and the jetting would be to suit that.
Adding oil leans out the mix and vice versus
They say 25:1 for added safety so I guess for a kilo run you could use less maybe 40:1 and therefore lean out the jetting to suit.
Do you have the original jet sizes for the Mod 50?
You might want to have an EGT proble/gauge to test that though.
http://www.vpracing.com.au/
http://www.racefuels.com.au/
http://www.etracingfuels.com
www.mjfmotorsport.com.au

[850cc racer]

well thats some interesting info. i will take that onboard...how would adding oil lean it out?.. 25:1/30:1 is where i have always ran my single throat 75 and havent had any probs.

[Powerabout]

If the fuel jets are passing a lot of oil then there not passing as much fuel.
The oil isn't really part of the mix so less fuel is the result of more oil
Just something to be aware of when altering your oil ratio

[850cc racer]

if you mix the oil and fuel as you need it and mix it well the jets are passing the "mix" not just oil or fuel..?

[Powerabout]

Yes but the the mixture now contains more oil.
The jets meter liquid subject to the air going past.
If the mix has more oil in it what comes out of the jet is more oil and less fuel per unit volume therfore fuel air mix is leaner.

Same amount of air has gone into the engine, same volume of liquid.( your mix)
its just that liquid is now made up of more oil and hence less fuel.
NB Ensure you dont get fuel with ethanol in it that will also lean it out.

[850cc racer]

ahhh im with ya bigger jets then

[Seagull 170]

I think you'll find that increasing the amount of oil in the fuel changes the viscosity & the thicker mix finds it more difficult to flow through the jets at the same rate.

Very few 2 strokes are ever short of fuel in the combustion chamber, they're usually short of the air to burn it!

[Mark75H]

Can you provide evidence? I use the same jetting for 32:1 and 24:1

it just isn't so

[Seagull 170]

Sam fill a coke bottle with oil & then fill one with straight gasoline, then time how long it takes to empty the bottles, I know this is a bit extreme but it's just to prove a point.

The difference between 40 :1 & 25:1 is only 15 ccs per litre, not a whole heap of difference, might well get away with the same jets, but try that with an early motor that runs 10: 1 & compare that to 25 : 1 & there's 60 ccs per litre difference, that might well need a jet change.

It's easy to get fuel into a motor just the cost of some jets, getting more air in there to burn it, costs a lot more cash.

[Mark75H]

I do not know of anyone using 10:1 or 12:1 at this time, so that is moot.



32:1 is essentially 3% oil ... 25:1 is 4% oil ... 50:1 is 2% oil .... the difference between 4% and 2% is virtually undetectable in both mixture strength for fuel/air and pouring viscosity

TRY IT and see, DON'T just guess or assume

[Seagull 170]

I do! & have.
Fully synthetic has sometimes required a smaller jet.

[Powerabout]

Ignoring viscosity issues does the following add up?

lets say you have gone from 50:1 to 25:1, (2% to 4%)
Therefore you have lost 2% of the fuel as it is now oil.

Just to compare the difference.
( assuming OMC C jet as in twin barrel, so size is number in thou)
There is a 1.67% area difference between a 060 and a 061 jet all things being equal the change of oil ratio from 2 to 4% has made a bigger change than one jet size to the mixture.

( anyone know the theory for flow in a pipe?)

[Seagull 170]

Test first the 060 jet with the 25:1 & see if it makes any difference, remember doubling the lube, might colour the plug.
Freds the man to ask, he seems to have tried every permutation.

[Tim Kurcz]

Dyno tests clearly show that more oil makes more horsepower. A good 55H was tested at 50:1 and delivered a respectable 39.9 HP. Doubling the ratio to 25:1 delivered a shocking 43.3 HP. We now understand why - the reasons apply to all two-strokes. Why do you think ratio makes a differece?

Also, the discussion about jet size -vs- oil ratio is dizzying. Once you settle on a ration and fuel type, the engine will tell you what it likes - provided you don't burn a piston first. Certainly an EGT is a nice tool, but to do it right you'll need one for each cylinder as the OMC triples are actually three one cylinder engines.

Finally, all my engines run 16:1 with Avgas. Why would I pick such a "risky" fuel? There are two primary reasons. There has been lots of discussion: Don't you know Avgas will burn your engine down because of it's high density. Hmmmmm. What gives?

[850cc racer]

wowsers so much discussion in my thread all about oil! there has been some good points raised. and some interesting data!:cool:

[Seagull 170]

Impressive 55H figures Tim, are the test results on the net?

[Fast Fred]

Mod 50 owner manual, first paragraph, inside cover, 50:1 mix uesin 100-130 octane:eek::cool:

[calvin]

So what is the reason more oil makes more hp in the 55h...leaner mix?

[Fast Fred]

compression i would say, lean does not make more power, lean melts pistons.:cool:

[genea01]

there was a test in the motorcross world were a mech tested a 50:1 to 32:1 and 24:1 and the 24:1 made more hp on the dyno and he said it was compression related and ring seal you can research back or google about 2 years ago and you should find it, they had the story in there magazine.

[Powerabout]

One guy I know in OZ who used to build and race (350's kneelers I think)
Used to practise from the reliable mix ( had cockpit adjustable main jets)
to lean and how far it would go before meltdown.
He said it was always worth a few postions if you were not leading
He said engine went from 18,000 to 24,000.
If it didnt make more power it wouldnt rev up would it?
They practised the distance so the driver knew when he could lean it out.
We must have all been in an outboard when it is running out of fuel..what does it do...revs up some more
For how long is the question.

I think the more oil and ring seal issue would be particular to each engine?
I guess you need to plug one into the 'spinatron'

Is it Jennings book or Bells where he leans the oil down till he sees scuffing then adds it back to find the right ratio. I guess this would be fuel, oil, engine etc dependant?

So when you run an E-tec on xd100 and re set the computer it makes less horespower?

The only recent test data I have read on fuels was in Hotrod and a chev.
a 9.5:1 carby engine and they ran it on high and low pump gas, av gas and some VP product.
The Vp guy promised them it would make most power on the VP and he was right.
He explained that even though the engine had low compression the race gas burnt faster etc( timing was set for each fuel) and hence also produced the best BSFC.
The av gas is not designed to do that so it didnt have the same improvement he explained.
Avgas will certainly stop detonation as thats what its designed to do, I guess knowing how it does that could be interesting.

Fuel density, specific gravity, btu's, bsfc, imep, egt all good stuff for a good thread.

I wonder what the last GP500 race bikes ran on?
You never see any smoke either.
The Japs seem to keep data on those very close to their chests as I can find very little info on them as I assume they would be the last big budget 2 stroke development, were they?

Avgas is also full of lead, I wonder if that is effecting anything?

[Seagull 170]

What I think Fred meant to say was " in competition engines lean doesn't increase power" as they're running as lean as they dare.

I have no doubt that in motors that are not running on the edge of heat distress a jet size smaller often helps, but as the fuel/air is a major contributor to piston cooling, running lean without piston ceramicing can cause nasty problems.

the fuel question is so dependant on what your running & which hull, where & how, you will get a different answer from everybody that comments.

I do like Avgas it seems to smooth my motors out, but prefer the higher heat output from pump gas, as the more heat the more pressure on my pistons.
That's one of the reasons I like plenty of oil in the mix better heat transfer from the piston through the cylinder walls, leading to slightly cooler & more dense crankcase contents giving a lower energy loss from crankcase compression.

Two-stroke high performance engine design & tuning by Cesare Bossaglia is a good read, almost as good as Jennings but slightly different but expensive & not available on the web

[Powerabout]

Can extra oil compensate for a lean fuel mix and vice versa?

I wonder if the E -tec alter the fueling when you change to 100:1?

I wonder what the oil ratio to power, graph looks like?
Is 1% to 2% a small difference compared to 2% to 4% power wise?

Why does extra oil make more power, it cant be adding to the explosion so....

Helping to seal the exhaust port to piston seal?
Does that mean the M31 will produce less power increase with more oil than a MOD 50?

Is it ring seal...so thats why OMC consumer engines have pressure back rings and their race engines dont coz they run double oil?

Graham Bell, Two Stroke Performance Tuning
available from here;
www.bevenyoung.com.au

Its a few years newer than the Jennings book
Has half a chapter on fuel and oil, much more then Jennings

PS If synthetic oil is any good shouldn't it produce the same power using less than the other oils?
Graham Bell says he could always produce more power with Castrol R ( avgas in all test)
I guess this is 80's test data?

Found this http://www.bridgestonemotorcycle.com/documents/oilpremix6.pdf
Jennings from 78

[Mark75H]

Ignoring viscosity issues does the following add up?

lets say you have gone from 50:1 to 25:1, (2% to 4%)
Therefore you have lost 2% of the fuel as it is now oil.


That assumes the oil has absolutely no fuel energy ... which is wrong. In general, lubricating oil (synthetic, mineral and vegetable) has about the same fuel energy per weight and volume as gasoline.


The question about oil ratio and power is a piston/ring & cylinder seal improvement ... more seal, more pressure = more power ... pretty simple

[Powerabout]

Mark 75

Power in the oil, I hadnt thought of that, makes sense.
So that adds to the story, how many BTU's are in each of the oil brands we use?
Does that means there is a 50 50 issue with dino oil more btu but synthetic less friction and better sealing?
and will the oil help or hinder detonation?
( assuming the synthetic cleans the engine via detergent process rather than a combustion process?)

too many questions

Cheers

[Seagull 170]

That's a very interesting point, has anyone seen any figures or creditable paperwork on this area.

What percentage of the semi particulate oil vapourises & joins the fuel & what stays as a condensate & does it's job as a lubricant? Some of it's got to burn or they wouldn't tell us it was low ash but a significant percentage must condense & assist the ring seal & to make such a mess in the exhaust.

With regard to the 55H power increases, almost 10% seems a huge jump.

This side of the Atlantic we see very few of the competition Mercs, so I have little knowlege of them, is 40hp the power output of a real good one, a OK one or a tired old one with slack rings?

[Powerabout]

lifted from www.motorcross.com



Pre-mix 101

OK, looks like it's time for a little pre-mix 101. I don't usually get into ratio discussions, because mix ratios are like religions to most people, and they tend to be closed-minded on the subject, but I'll put in my $.02 here anyway.

There is a prevailing myth that less oil is better, and that the oil in the fuel is what lubricates the engine. Both are wrong.

*less oil is better* People think that if they have a plug fouling problem or a lot of spooge, they need to run less oil. Wrong! Both problems are caused by rich jetting, and have nothing to do with the mix ratio.

*the oil in the fuel is what lubricates the engine* The engine is lubricated by the residual oil that builds up in the crankcase. All the oil in the fuel does is replenish this oil.

The best way to determine if you are running enough oil is to check the level of the residual oil in the crankcase. If the ratio you run leaves enough residual oil in the crankcase to cover about 1/8" of the bottom of the crank wheels, then you are fine. If you don't have that much residual oil in your crankcase when you pull the top-end off, you aren't running enough oil for your riding style and conditions.

With that said, to have that amount of residual oil in the crankcase at 50:1 (a ratio made popular by magazines and oil bottles), you can't be riding very hard, or your bike is jetted richer than necessary simply to deliver enough oil. I arrived at 26:1 for my bike with my riding style because that is the amount that gives me the proper amount of residual build-up. Small-bore engines require greater oil concentrations than larger engines to achieve the proper amount of residual build-up, because they rev higher and have higher intake velocities. Along the same lines, someone that pushes the engine harder, and keeps the revs higher, also needs to use higher oil concentrations to achieve the proper residual build-up.

To understand why the residual oil is so important, you have to understand what happens to the oil in your fuel when it goes into the engine. While the oil is still suspended in the liquid gasoline, it can not lubricate anything. It has about as much lubricity at that point as straight gasoline. When the gasoline enters the engine, it evaporates, dropping the oil out of suspension. Now that the oil is free, it can lubricate the engine, but it must get to the parts to lubricate them. The way it gets to the bearings and onto the cylinder is by being thrown around as a mist by the spinning crankshaft, and the droplets are distributed by the air currents moving through the engine. Ever wonder why there are two small holes in the transfer port area of the crankcase, right over the main bearings? These are to allow some of the oil droplets being flung around inside the engine to drip down into the main bearing area.

Some of the oil eventually makes it into the combustion chamber, where it is either burned, or passes out the exhaust. If the combustion chamber temps are too low, such as in an engine that is jetted too rich, the oil doesn't burn completely. Instead, some of it hardens into deposits in the combustion chamber, on the piston, and on the power valve assembly. The rest becomes the dreaded "spooge". The key to all of this working in harmony is to jet the bike lean enough to achieve a high enough combustion chamber temperature to burn the oil, but also still be able to supply enough oil to protect the engine. If you use enough oil, you can jet the bike at it's optimum without starving the engine of oil, and have excellent power, with minimal deposits and spooge. At 50:1, you simply can't jet very lean without risking a seized engine due to oil starvation, unless you're just putt-putting around on trails without putting the engine under much load.

With the high oil concentrations that I use, I tend to get far more life from my cranks and rings than most of my friends that run leaner oil ratios. The high oil content also produces better ring sealing, so more of the combustion pressure is retained.

One small point. No one ever broke an engine by using too much oil.


Pre-mix ratios and power production

I have run Dyno tests on this subject. We used a Dynojet dynamometer, and used a fresh, broken in top-end for each test. We used specially calibrated jets to ensure the fuel flow was identical with each different ratio, and warmed the engine at 3000 rpm for 3 minutes before each run. Our tests were performed in the rpm range of 2500 to 9000 rpm, with the power peak of our test bike (a modifed '86 YZ 250, mine) occuring at 8750 rpm. We tested at 76 degrees F, at 65% relative humidity. We started at 10:1, and went to 100:1. Our results showed that a two-stroke engine makes its best power at 18:1. Any more oil than that, and the engine ran poorly, because we didn't have any jets rich enough to compensate for that much oil in the fuel, and the burn-characteristics of the fuel with that much oil tended to be poor. The power loss from 18:1 to 32:1 was approximately 2 percent. The loss from 18:1 to 50:1 was nearly 9 percent. On a modern 250, that can be as much as 4 horsepower. The loss from 18:1 to 100:1 was nearly 18 percent. The reason for the difference in output is simple. More oil provides a better seal between the ring and the cylinder wall.

Now, I realize that 18:1 is impractical unless you ride your engine all-out, keeping it pinned at all times. But running reasonable ratios no less than 32:1 will produce more power, and give your engine better protection, thus making it perform better for longer.

[Mark75H]

Pretty good, except I would give credit to outboard mfgr's operating instructions for promoting 50:1 ... a tidbit that would add to his overall good understanding.


There might be a correlation between motor size and the load of oil they will tolerate and he may be right about velocity thru the system being the key. Merc recommended 18:1 for all the racing motors from the V-6's on down; Hot Rods were famous for using even more ... but then again they were using the crankshaft rotary valve set up that probably needed extra oil to help seal it.


On 2 strokes oil lubricates rings and piston skirts mostly from the sides and bottoms, you don't need to worry about oil lubing from the top after combustion. On a 4 stroke unless you add oil to the fuel as "top oil" they get no top end lube at all and can run for tens of thousands of hours with no problem.

Synthetics don't have cleaning detergents, they are just cleaner and more pure. Dino oil only has the worst junk removed from it, it is still a mixture of "stuff" when used as 2 stroke oil ... synthetics are chemically built up from alcohols and only contain the chemicals the makers want in them.

There are a lot of things regarding the octane & combustion related to oil, I'll post more later

[Tim Kurcz]

Howdy y'all.

Sorry to have missed the fun this week. Lots of work and too little time. Also, for some reason I'm not getting bounce-back email from BRF! Hmmm. better complain to the management!

Anyway, it's great to see such lively, informed discussion. You've all identified the answer(s) before I could reply. Sealing the piston rings is very important, but don't forget the reeds and inter-cylinder labyrinth seals. These close clearance "seals" all perform better when well lubed.

The referenced MK55H dyno test proved opposite what stock drivers told me in the 1970's - it was a relief to see conclusive data for myself many years later. While on the subject of beach racing, another popular tip was to undercut the inter-cylinder seals to keep the crank from dragging. I'd like to know see the data where that actually helps. Lemme see: increased clearance = decreased crankcase pressures due to internal leakage and a somewhat undersupported crank. What part of this makes sense?

The oil "river" discussed is critcal to engine life as well. As a young Mercury mechanic, I was taught to run race engines with as much oil a possible without fouling the plugs off the beach - the engines last longer. And somewhere along the line it was explained that there is more heat energy in oil, hence more oil more power. The only reason to run less oil was to reduce smoke and improve resistance to fouling (for fishing engines). Most likely the thin ration were developed for sales & marketing bragging rights about the least cost-to-operate engine.

Now for fuel choice. Oxygenated racing fuels will deliver more power than Avgas - for a while. Most degrade rapidly once the sealed containers are opened and misbehave accordingly. The same goes for any pump gas (Turbo Blue, etc). One "pump" gas exception is Avgas. Spec's call for two year stability in an opened container (such as an aircraft fuel tank). After losing a few heats traced to spoiled (canned) racing gas and (pump) Sunoco 260, I switched to Avgas. You can buy it anywhere, trust it to deliver consistent behavior, and never blow the meter even when it's hot. The rule of thumb is to tune for the fuel you run, don't make any changes, and go have fun racing. Sadly, it's taken me several boxes-o-pistons worth of experience over thirty-some years to arrive at what works consistently.

There's my 2-cents worth. Great thread!

Tim

[Popa Sam]

Howdy y'all.

While on the subject of beach racing, another popular tip was to undercut the inter-cylinder seals to keep the crank from dragging. I'd like to know see the data where that actually helps. Lemme see: increased clearance = decreased crankcase pressures due to internal leakage and a somewhat undersupported crank. What part of this makes sense?


Tim

Someone told you part of the story, as usual. Most wont tell you something that actually increases performance. That's why it's good entertainment to read questions and replys on these forums. If someone had a big secret for performance enhancement, do you think they would tell you???

[Tim Kurcz]

There's no doubt that alot of engine bull%$#& floats around the pits. But I'm continually shocked at the influence thereof. I've had no fewer than half a dozen stock and mod racers demand I bore .005-.006" from the ID of Merc reed cages despite my protest. Hey they heard this from so-and-so, so it must be right!

BTW: You're right - builders like me keep the very best tricks for themselves. The difference is I choose to communicate enough solid information to keep the racers from frustrating themselves: The objective is to have fun driving and grow the sport.

[Seagull 170]

Do you stuff reed cages Tim.

[Tim Chance]

Merc recommended 18:1 for all the racing motors from the V-6's on down; Hot Rods were famous for using even more ... but then again they were using the crankshaft rotary valve set up that probably needed extra oil to help seal it.


when I first started racing most everyone I knew used Ace-O-Speed. It came in two mixtures MAB (20:1) and CFX (16:1). Mercs ran MAB while Hot Rods ran CFX and I never knew why until now.

[Tim Kurcz]

For Seagull & others,

I've been operating Bud Parker's machine shop for 10 years after having worked with him 11 years prior. He taught me pattern making; so castings are poured for complicated shapes. I use an aviation certified welder for fabricated structures; TIG, MIG, Heliarc, and gas if needed. A local plating shop is used for zinc or electroless nickel coatings. Powder coating is also available. A CNC machine shop is used for repetitive devices.

I personally build 8-10 race engines per year (and numerous sub-assemblies), and specialize in one-offs to take advantage of windows in the rule books. So, you betcha, I can stuff cages - provided the architecture allows.

[Powerabout]

thanks for the great posts.

So what we can take in is;
as much oil as you can
avgas all year
race gas for the one off event

Now we just need the BTU of the oil comparison,
who use TCW -III and who uses API-TC?
and
Mineral
Blends
Synthetic

[Seagull 170]

I'm not sure it's as clearcut as that, there's a whole lot of other factors that could affect your conclusion.

Motor design, types of bearings, cylinder wall type/condition, number & style of rings/piston design, operating rev range, piston/rings/borefit, combustion pressure/temperature & exhaust style, & possibly a few more.

What we all need is a dyno & a lot more testing.

Thanks for that Tim, what I was after was your views on reed cage stuffing.

[Tim Kurcz]

No. 6 Fuel Oil (used motor oil) = 150,000 BTUs/gallon
No. 2 Diesel Fuel = 140,000 BTUs/gallon
Kerosene = 135,000 BTUs/gallon
Jet Fuel = 130,000 BTUs/gallon
Biodiesel (B20)= 128,000 BTUs/gallon
Gasoline (mid grade) = 125,000 BTUs/gallon
Aviation Fuel (Avgas) = 125,000 BTUs/gallon
Ethanol = 85,000 BTUs/gallon
Methanol = 63,000 BTUs/gallon

This information was obtained from a 15 minute web search. I couldn't locate anything specific to 2-stroke oil - yet. It would appear that the heavier the oil, the more BTU capacity. Here's an interesting read:

http://www.sea-doo.net/techarticles/oil/oil.htm

[Tim Kurcz]

"Cage stuffing" is use primaily as a transition device from a single barrel carb to a wide reed cage. They are common to snowmobiles and dirt bikes where one carb per cylinder enables the opportunity to use a range of venturi/throat sizes. The objective is to improve the flow through the cage.
Indeed they work. Is this the type of stuffer you were thinking of?

[seaward]

I am not really good with percentages. But in 39 yrs.of o/b and app. 25 yrs. of h/p work I have found that Maxima 927 in generous amounts works to increase longevity and a real top end increase in the same engine setup. A direct fuel increase is imperative in these situations.
Hal Broomes
PS: It only works good if you keep it wound up. Very little idle.

[Mark75H]

Thank you for that research, Tim.

I hope everyone has taken note of the relatively narrow BTU range of the fuels and oils (other than the alcohols). They all fall within 20% of each other. Now factor in the narrow dilution range of 6% to 2% we use for lube oil ... any difference in fuel energy from oil is negligible, and if there is a difference, it is likely that oil adds energy to the combustion process.


A question that was asked earlier was relevant: does oil affect the octane rating of gas in a negative way?

The answer is most likely yes ... with a "but ..."

The but is ... we aren't putting that much into the mix.

If lube oil was real crap had an octane rating of 60, mixed with 89 octane gas at 25:1 the end result mixture would be 86 octane. Before you freak out about this ... you've been running your motor this way since it was new ... 86 finished octane is all it needed. At 50:1 the octane performance would be degraded to 88.5.

These degrades are already accounted for by the manufacturers in their gas recommendations.

Now for a ringer in the game ... synthetics

Most synthetics have additives to significantly suppress flammability, that's why you see often see liquid synthetic oil dripping out the stack or stinger of a motor running synthetic. This is not the majority of the oil that was mixed with the gas or alcohol ... just a small amount of it. Any oil that was sticking to the edges of the combustion chamber ... especially in a "squish band" or dammed area may not have exceeded the ignition point with the flammability suppression additive (of about 1,000 degrees) ... and when the motor is not running wide open, combustion temperature can be much lower than normal (for a race motor). So, even though most of the oil was consumed with the gas, some dripped out as unburned liquid. Mineral oil and castor oil have an ignition point some where below 200 degrees if I am not mistaken; where unsuppressed synthetic is around 300 degrees.

Enter a third player ... there is a product on the market that claims to be both lubricant and octane booster. It is a synthetic based oil. Guess what it does not have ... oh, my ... this product does not have the high temp ignition suppressant.

My theory about this product is that by accident this manufacturer discovered that the flammability suppressant decreases octane and the base synthetic increases octane. Simply leaving out the additive that suppresses ignition from the 300 degree range to the 1,000 degree range, lube oil became octane increaser. I think they sell it for about $130 a gallon, but say you can use it in addition to your regular oil at your regular ratio something like 60:1 or 50:1 to gas and get decent octane improvement.

I would really like to see some of this junk tested to see if it really provides results or if it is simply a case of it being used by guys who think their motors need a lot higher octane than they actually do (and it is doing little or nothing).

[850cc racer]

im liking all this info in here.

i ran the motor today... it sounds so crisp. amazing how good the mod50 exhaust makes them sound... i will be giving her a run up on wednesday night to see final numbers.. she hasnt had WOT yet.

so far she has done everything i want..:cool::eek:

[Powerabout]

Great post Sam

I wonder what the octane or cetane rating of outboard oil is?
Would a diesel run on it and would that be a dyno test to see what the TCW oil does?

Cheers
Powerabout

PS we were always taught by Merc and OMC, the longer you leave the oil mixed with the fuel the lower the octane ratings goes as well?

[Mark75H]

PS we were always taught by Merc and OMC, the longer you leave the oil mixed with the fuel the lower the octane ratings goes as well?


I've never heard that. I wouldn't have a theory about it, other than the regular "old gas" situation where some of the better higher octane components WERE some highly volatile ingredients like butane. If the gas was really dependent on the butane and you let it evaporate ... the longer you left it, the lower the octane would be. Some components would also oxidize while in the mixture (at the surface where exposed to oxygen in the air).

Since new cars are for the most part fuel injected, vapor pressure for gasoline is lower than it was in the past and less butane is used. Unfortunately, since more cars have fully closed tank vent systems, more of the junk that oxidizes when exposed to air can be tolerated by cars ... gas companies put it in because its OK to use in new cars ... the primary market.

A Diesel will run on any flammable liquid you can properly get thru the injectors. Some early versions used coal dust mixed with water ... just because they could use an otherwise waste product. Some of those things had injection systems larger than the rest of the engine; not practical in a vehicle, but great to replace a steam engine or mill wheel.

[Powerabout]

Could be Sam, I'm talking service school info of 20 years ago in Oz.
We went unleaded in 87 by the way, evaporative emissions regs came in, in the mid 70's
(ADR 27a was the regulation, strange the things you remember from your younger days?)

Looks like boats need that reg now with ethanol exposed to the air
Isn't the US doing that next year?

[Seagull 170]

Was that benzene or butane Sam?

[Mark75H]

Benzene is the foundation of the aromatic family of chemicals and has not been an ingredient in gasoline since about 1950. It is both directly highly toxic and highly carcinogenic. It is not especially volatile, it boils at 176, butane boils at 31.

[Powerabout]

Shell
Admitted that there is a small amount of Benzene in their fuel in Singapore
when describing their fuel that they blend for the Ferrari F1 team and how similar it is to V Power sold at the pump.
( F1 fuel cannot contain any additives that are not in EU pump gas, so there must be benzene in EU gas?
2009 F1 spec allows 1% by weight)
The tree huggers had a go at them and they said the level is so small its not dangerous?

http://argent.fia.com/web/fia-public.nsf/130A104E1769D120C1257617002D4CAE/$FILE/Stable%20Technical%20Regulations%20-%2024th%20July%20-%20CLEAN.pdf

[Fast Fred]

Lean, most likely ain't goin to make the back to back, flat out runs. never did a run a kilo but as i understand it, you gots to flat out, full steam when you cross the startin line. then you got 15mins to turn it around and do it again. lean most likely ain't goin to make it:eek::cool:

[194265]

I have been following this thread with much interest, and am surprised a the concern and interest in oil mix. From 1968 until the fall of 1973 I worked snowmobile engine lab at OMC and ran many dyno tests there. At that time two cylce oil was rate at TWC-II. All dyno runs, unless indicated otherwise, where run at 16:1. We did run make some runs at 24:1, 32:1 and 50:1 oil mixes and noted no change in power. We did noticed however, a rise in temperatures as the oil was leaned out. Not a big jump but 20 to 25 degrees from 16:1 to 50:1. I then went to Mercury in the fall of 1973 and left there in late summer of 1974 (got divorced). I worked in Advance Research and worked on Snow Twister snowmobile engines and C-6 outboards. We ran all dyno checks on Aviation gas and 18:1 oil mixes. I run all my modified outboards at 24:1and my stockers at 32:1 mixes. I hope this helps.

[formeone]

mmmmm,,,wow!!! some great info,,,,, just my .01 cent.... i would have to agree with tim,,, the most,,, with my 32 years raceing,,, and a bunch of records in the old days,,hehehe,,,, i always ran av gas mmm and reg 2-stroke oil,,,, merc or evinrude and not synthetic,,, av gas was and is always consistant 100 octane ,,,, slower burning of course,,, cause less air at altitude,,, but i always corrected with timeing,,,,, then ran the coldest plug could get!!! old trick learnt from bob wort and ed karelson,,,,, i personaly runmy 3 holer on 100 or 108 octane, fuel/gas,,, then one quart to 5 gallons,,,, soo what that about 16-1??????mm,,,, learnt fromtheold timers and it works,,,,,, when we set the d-stock kilo and comp record with the 44xs,,,we ran 2 quarts red line to 5gals,,,,mmmmmm.....was messy but haaa we set records,,, when i set 850 kilo at 104 mph was av gas and evinrude oil,, quart to 4 gals..... stillr un the same mix seems to work have gone leaner on oils,,,, just doesnt seem to be as good.... personel note that i think there is alot of additives in theoil these days,,,, and it adds hp,,,, hell see if it passes fuel meters,,, youd be surprised,,,,,,,the meter readings

[formeone]

also to your kilo try with your mod 50 motor,,,have you blue printed your bottom of the boat??,,, no woopdy's nice and flat?? as possible??... also i would think you need to spin the motor over 8k rpm,,,as we all doo when we race them{ the49.9 cubers} around here,,,,, that and throoo some timeing into it,,, but be careful with it that what melts 2-strokes down the most,,,,,

[850cc racer]

Hey Formeone.. thanks for the info. i have done everything i think is right.. the bottom of the boat i havent touched, i think the boat doesnt need touching, she did 75mph with a single throat 75 just fingerported.. 2-1 ratio and 12x23.. im adding a tonne of power up top im keeping the same prop.. i have a few props the two i will choose from are twins except one is thinned, the thinned one is good for an extra 2.1mph. :eek: im changing the ratio to 1.85-1 im taking it out tonight (in about 9 hrs) to see what it does..

will post photos and readings later.:eek::cool:


Rob

p.s. todays going to be a long day at work!

[formeone]

if ya put straight edge under bottom just to check,,,, it only take 1 minute,,, then ya know for sure,,, takes less hp to push a straight bottom than a hooked one????...

[formeone]

also hold straight edge on side of gearcase,,, see if straight,,,you might be surprised,,,any scratches or whoopdy"s on side of gearcase sucks more air to prop or pushes water away if cae not straight,,,,,,i re conture raceing case even so we handle and go faster,,,,,

[Seagull 170]

194265
Where were you measuring those temperature changes?
coolant, plug, exhaust gas, or are we talking air cooled.

Why were the manufacturers running avgas? wouldn't this give answers that differed from the 99% of the production units that only saw pump gas.

It would be fasinating to read of what you remember of the manufacturers testing methodology.

[850cc racer]

also hold straight edge on side of gearcase,,, see if straight,,,you might be surprised,,,any scratches or whoopdy"s on side of gearcase sucks more air to prop or pushes water away if cae not straight,,,,,,i re conture raceing case even so we handle and go faster,,,,,

Cheers mate i will do that for sure.. ill slide her back on the trailer a little.. as you can see from my pic she sits perrrrfect.

the gearcase has two very little marks in the side of it.. i took all the paint off it.. i will check that too (straight) and fill these two marks in..

[194265]

The thermocouples we used where all buried in the alum. The temps that we took where located at the Spark plug boss and four other places right above the exhaust port and around the cylinders. In other words at the back, the two sides and at the exhaust port. These where air cooled snowmobile engines (all OMC engines). Again the biggest increase in temps was 20 to 25 degrees and was measured at the exhaust port, which was between 420 degrees and 450 degrees. Please understand that this is not the exhaust temp but the cylinder temp at the exhaust port. The other four points showed temp rises also, but at lesser amounts. Like I said all dyno runs at OMC unless told otherwise where run at 16:1 oil mix (OMC) oil) and regular gas. Would also like to state that until 1972, all OMC snowmobiles where to be run on 24:1 mix

At Mercury the Temps where measured with copper washers connected to thermocouples and placed under the spark plug. We used 18:1 oil mix (Mercury oil) with Avgas because they where both racing engines. The snowmobile engines (Snow Twister) where Canadian built Kolhers air cooled engines and the C-6 was of course water cooled. I was not there when the 1976 Snow Twister came out, it was liquid cooled.

[Seagull 170]

Thanks that's fascinating, was a reason ever reached to account for these rises & is it safe to assume that due to your location all temps are in F?

All the interesting info was garnered in the pre PC days & getting a glimpse of those hand written log books is very unlikly, even if they haven't already contributed to global warming.

[194265]

Thanks that's fascinating, was a reason ever reached to account for these rises & is it safe to assume that due to your location all temps are in F?

All the interesting info was garnered in the pre PC days & getting a glimpse of those hand written log books is very unlikely, even if they haven't already contributed to global warming.

The first OMC snowmobile was built in Canada in 1965 and Engineering was moved to Milwaukee in late '66 or early '67. It was located at the new assembly plant on 64th street, four blocks north of Capital DR. It was then relocated in Waukegan in the fall of '73, I think that was Edgar Rose's idea. I know all this is off topic, but since you are interested, I don' mind. Well anyway we all know what happened to engineering in Waukegan, it is among the late and lamented. Getting back to your questions, we ran the oil mix test one ratio right after each other to control the tests. We believed that the addiction oil helped cool. As far as test results go, I have copies of many tests we ran. We ran one engine that Mark75 would be interested in. It was a 500 cc Koing outboard of which I have copies of the dyno run and engine survey. All temps where read in F and not C.

[Seagull 170]

194265
Well I for one, can't wait for you to start a new thread & let me have a look at that Konig stuff.

If you lived a bit closer I'd be over trying to photocopy it for bedtime reading.

If we don't get this stuff on the net, when we go all this information will be gone, when that happens all that will be left is guesswork, conjecture & BS!

[Powerabout]

850

hows the MOD going?

[850cc racer]

Hey well i had a few overfueling issues. and wasnt due to pressure/flow etc.
ive since fixed the issue and she now revs up like it should :cool:
i missed out on the kilo as i didnt have her right for it.

taking her out tomorrow for her first run up. see how she preforms.

will post up speeds and photo's

850

[850cc racer]

did u get that mid powerabout?

[Powerabout]

did u get that mid powerabout?
Wife will pick it up today, so i'll let you know.
Thanks

[Fast Fred]

hey 850, hows she lookin:cool:?

[850cc racer]

shes looking real good fred.

however its raining here today so no testing for me.:mad:

[850cc racer]

okay well i have just taken her out.

i have ran her in and turned her up.

i have put my other omc box on,... im needing clarification on ratio. its not 2-1 it is less maybe 1.85? 1.78? what did they come out in? can anyone help with that?

she spun up to 7 with a 12x23 long tube cleaver on. shes still on the FAT side but im a leave her there. fat is good for me.

im stoked with the performance.

850

[Popa Sam]

I'd been following this wondering where you found a 2:1. Never know what the boys across the pond may come up with. If it's the Sprint or SST60 case it's 15:28/.536 /1.8666:1.

[Powerabout]

Same here

I know a few guys here that custom made gears in some classes
Just gave you the edge sometimes especially when the opposition checks out your prop and think they got ya sussed.

pitch x rpm
__________
gear ratio x 1056

=theoretical speed

[850cc racer]

Hmm i dont think these are custom gears? I have the matching mid. Was made in belgum.
Working it out roughly its 80mph. Im racing this sunday. Will carry gps.
This thing has a tone of punch and exhaust is Crisp as. Such a good note.

[Powerabout]

Did you use pump gas at 25:1 or something else?
Good luck

[Fast Fred]

Such a good note. ya it did:eek::cool:

[850cc racer]

na mate avgas. Thick is the ratio.

Going back to 2-1 in the gearbox to see that 7500rpm we want

amazing how good the exhaust sounds hey fred!

[Fast Fred]

2:1 is quicker than 1.86:1, but not faster,maybe slide the Moda up on the transom with the 1.86 foot.:cool:

[850cc racer]

Yeh thats true im thinking 2-1 7500rpm 12x23 80mph.

When the kilo comes round again 1.86 and slide it up then

racing sunday will be good.

Watch this space

[88workcar]

Get some VIDEO and post it for us.

[genea01]

hey 850 any up dates for us or any videos what gas did you find to be the best for you and did you go 25:1 on your oil

[850cc racer]

well videos that aint happening. my mum (MOM for you fellas) did some footage and the darn video player wont play it back.

first race i narrowly lost :mad: due to leaving the 1.86 bag on she couldnt wind up quick enough..was a rough ol day had the trim working overtime. i see its better to keep her nailed and just trim if need be then backing off :eek::D
i saw 72mph on the gps with the 1.86 on that was low, i think if i had 2 miles to wind her up well who knows :eek: the thing SCREAMED with the 2-1 pulling well into 7's but didnt have gps with me.

i changed gearboxes and made up 40 seconds in the handicap :eek::cool:

we run again in january. ill make sure i have footage and also gps her

im also about to go start here up wash her out and change fuel pumps. not happy with the one i have.

850

[genea01]

well anything new for us 850 how is everything going

[850cc racer]

hey.. not as yet. i have a new fuel pump and reg on the way. didnt like the old one. theres a couple of little things im doing just to see if that makes a difference.. havent had it out since the last race meeting. once i have my fuel pump and reg ill then start doing a few checks.

ill make sure i have footage from next meeting :cool:

whats news over there?

[850cc racer]

well its 12:20am here. i have my alarm set for 5am to get up and strip the mod 50 down. its going to be 32degress here tomorrow (86F for you folk) so im going to get it done early. just have a few things to do to her to let her perform how she should. will be interesting to see how she goes after this.

hope everyone has a wicked NYE.:eek:

850

[850cc racer]

what a flat out day. got done what i wanted to though! will be interesting to see how she performs now :eek::cool:

oh yeh its 2010 over here in aussie land :D

have an awesome nye all!!

850

[genea01]

850 what else did you so to ur motor or is it top secret right now

[850cc racer]

hey... well its not that top secret, its more something that was overlooked.. once i run it ill let you know the outcome. it could be a considerable increase.

having a brand new mod 50 case means i can change to how i want it.. not how the 15th person who owned it before me did it:eek:

happy nye over there in usa.

850

[850cc racer]

laying down the law:eek::cool:

[Powerabout]

Nice

Is that a sst 60 cowl and lower pan?
Someone making them in OZ?

[850cc racer]

its the same as them. i have a few of them. easily make a mold

[Powerabout]

ok great.
I'll be looking for one soon

[850cc racer]

i have one here with nothing on it im going to flop a mold from.

the base ill copy from the one in my avatar.. it follows the steering bar.. really good base that one.

850

[Powerabout]

Once you've done the cowl, how about the whole boat?

[850cc racer]

haha well i was going to try and find the molds for them. i reckon they'd be worth getting hold of. that thing sits so darn perfect. it was rough as on the weekend and she was sitting like that pic all weekend and never felt like going over.. except once.. maybe that was after i won the big race and thought id air it out over the line :D:eek::cool:

[Powerabout]

Whats the history of the molds
Did Steve M sell them or what?

[850cc racer]

the molds are in qld somewhere. theyve made a few from them in the last couple of years...

[plasterer timgarfield]

try creek marine last i heard they had them tim

[plasterer timgarfield]

rob you got a mold done for that cowl yet

[formeone]

haaaa 850..... what kind of speed did you finally see out of your boat with all the new motor and all you did???? just curious....

[850cc racer]

Hey mate im still playing with it getting things right.. I still have to mod the tuner. Get jetting correct as its massively fat.. Ive seen 75mph but thats only pulling 6900... jets are on back order.. saturday im shortening the tuner to 'tune' her in to get that 7400rpm +

[formeone]

i sodder my jets and then just drill them the size i need,,, i measure a drill bit with verier calip and select one i eant and just hand drill them,,do you have to run tuner in the center section??? if not what about one of tims exhaust or one likemine up the top seems would breath better,,

[850cc racer]

Ive thought about soldering them but would rather just buy the right size...
Well we do run cowls and exhaust through the midsection.. I may buy one of tims exhausts but still deciding.. I want to get it spot on before changing anything..

[850cc racer]

everytime i try to get on it the mod 50 makes her wheel stand :eek::cool:

[850cc racer]

and it sits just perrrrfect

[Powerabout]

nice
looks like the nitrous button was accidently hit

[850cc racer]

hahaha very very rough at the regatta grounds here yesterday.

[Fast Fred]

:cool:

[Tim Kurcz]

Wha-whoo! Looks rough but the boat flys strait. Great photos. How did you place?

[850cc racer]

Hey Tim..1st in pole boat start. 1st in handicap made up 1.10mins :cool:

[Fast Fred]

850, how is she about gettin on plane, sendin mine out for new sleeves, wanted to know if the port hight should be adjusted:cool: it's out of hear Thursday.:eek: " My kilo Moda ":cool:

[850cc racer]

Hey fred pops on the plane no issues. Its only if its chuggs around off the plane for a while that it does bog down a little.. I always keep her up and moving around if im waiting for a handicap start but straight off trailer and on plane no issues.

Im going to take her out for a spin later in the week see what she does now i have changed a couple of things... It was to rough to tell on the weekend. Only got 1/3 throttle.


850

[formeone]

haa 850 you running surface gap plugs or j gap??? mine seemed to luv the surface gap plug alot better... just a thought

[genea01]

how is it going have any new updates whats new with the motor

[850cc racer]

Hey mate, i raced it last weekend very very rough so i couldnt get onto it.

im hoping to be able to take it out and test it during the week to see if the couple of changes i made makes the difference im looking for.

its been so long getting things right. however patience is whats needed.
happy with the progress so far. i know that once its right it'll be awesome:cool:

850

[850cc racer]

its been a bit quiet in here. ill be getting her out tomorrow and start her up. i race on sunday, generally a little rough where im going, the next weekend is back on home soil, if the weather is good sunday ill be able to open her up and see what she does :cool::eek::eek:

850

[850cc racer]

so after 6 years i think i can finally wheel this thing :eek::eek::cool:

[Powerabout]

Great photo!

[Fast Fred]

:cool:

[genea01]

looks good

[850cc racer]

thanks guys. she sat that way all weekend. until i was heading north, massive hole in the water from the boat infronts wash.. didnt see it til last minute, jumped on in button however and up she went i ended up facing S/E.. closet i could get with out going over.. i got it going again as i was way infront however coming down home straight lost spark for some reason. didnt hurt boat or motor. i did however smash clear plastic shield on hood. hit pretty hard :eek:

850

[50hptiller]

got'er air'd out good 850. when do we get to see some video of that thing?

[850cc racer]

hey Fiddy hp. ill try to get some good footage at the next (last) race meeting of the season.

check your pm's man that 13x27 is on its way to you. i hope your built like a small ox. that thing will take some holding.

850

[50hptiller]

hey Fiddy hp. ill try to get some good footage at the next (last) race meeting of the season.

check your pm's man that 13x27 is on its way to you. i hope your built like a small ox. that thing will take some holding.

850

shhhhhhhhhhhhh.......... it was top secret...lol...i am fat though

[JAKE62]

Hey Racer,
I didn't read all 18 pages of this but good luck on the kilo run. Is there a weight rule over there? If not it's within reach.
I set the NOA record in 1985 with a 49 inch motor on a 13' Critchfield.
The record was 85.400 MPH I made a one way pass over 87.
There were no mod 50 parts the rules then was to modify stock parts.

Good luck, Larry Davis

[850cc racer]

Hey mate, the kilo run was back in november, unfortuneately i didnt get enough time to run/tune the motor, so i missed out on running. however have since fixed it..

i have ran it for about 6 race meetings now, i havent really played with it props, jetting etc needs leaning off a little.
the motor is very strong and pulls really well! it does 75mph around a course, i dont have anyone catching me so havent had to "make" it work..

thats a massive speed to be doing!! would you share gear ratio's props used etc? what sort of rpm?

i have a simalar motor to what u speak of, 49ci single throat front and fingerported that pushes the boat to 75mph aswell.

driving these little monos is the BEST fun!!

thanks for posting!

850

[Powerabout]

That record should be a stock 75 with 15" and a Nitro lower
can shave the cyl head and rejet
and thats it I think?

[formeone]

haaa 850,,,, was wondering if youve tried a 12" prop??? and increase your pitch,,,, se tunnel andthe other race boats over here i know run a 12*25 or so!!! check with ron hill,,, he deff would know,,,, more ime sure ....just a thought...

[JAKE62]

Yes it was a 75 nitro gear case with stock gear ratio. The only props I had was 23's so I borrowed a couple of 25"s I don't remember the diameter, it was turning around 7300 the best I remember.
The rules then was you could do what you wanted with the stock parts.
"ported with cut head" and run on gas

[850cc racer]

powerabout: the rules have changed over the years from what i can gather, and have now locked and loaded those records in place.
the 1250cc open hull was set with an FT motor.
several different people have told me the 1250 mono record was set with an FT
its an interesting one.

formeone: i run 12x23 long tubed cleaver, 2-1 ratio.. when a kilo comes around again ill play with 2.4-1 (stock) ratio and also my 1.87-1 nitro. see what combination works best.

jake: that is fair going!! what ratio was that one? i like the critchfields nice looking hull!

850

[JAKE62]

Its a 15:28
<a href="http://s763.photobucket.com/albums/xx279/JAKE62c/?action=view&current=extremedc13running-thumb.jpg" target="_blank"><img src="http://i763.photobucket.com/albums/xx279/JAKE62c/extremedc13running-thumb.jpg" border="0" alt="Photobucket"></a>

[850cc racer]

hey mate that thing is sitting perfect!!!!! its make me want to get mine out and take it for a spin see what it would do set up in kilo form!


thanks so much for the pic!!!

850

[850cc racer]

update: just did 78MPH:cool:

starting to come on nicely. still a few jetting issues to sort out needs to be leaner.

850

[formeone]

mmm and i just ran my 49er at 100mph testing at about 2400 feet above sea level,,,honest,,,just a teaser guys,,,, but did hit 100mph,,,,, keep digging,,

[850mono]

With the specs you gave, 1st post I find potential speed to be 70.79mph. Im not trying to cast doubt tho just to say there are variables on the boat beyond arithmetic while #s are cut & dry. The 1.85 :1 ratio with the 12 x 23 prop @ 6500Rs could potentially go 76.4. I dont know much about the powerhead except to say it will need to produce power at much more rpm. for that 83mph+ mark. At 2:1, 23P youll need a minimum of 7700 Rs to reach 83.8 & thats before subtracting slip/resistance that can vari from about 90% [very efficient] or less.
What I do to get these #s is Pitch times RPM divided by 12, times 60 divided by 5280, times Ratio. [.5 in this case]= Potential Speed. To get ratio I divide the low # of gear teeth by the high #. for instance Yamato 14/15s = .933:1 using .933 to multiply. Best of Luck with that run for the record. :cool:
Hi Rob I dont know where you have seen 75mph maybe behind your car! I built the boat and my mechanic Alan Downes built that motor it was the fastest 850 cc mono in Queensland Australia, I have been racing for a long time and have a lot of experience with 5 championship wins as you know, the best speed I ever saw was 71mph but in race trim 69 / 70mph when the motor was fresh and the boat was new and the bottom had just been straightened . To gain 4 mph with the same motor is a big ask. Also the 1250 record of Steve Medaris's that you want to beat was with a standard sst60 and any motor used to attempt to beat the record must be standard production and under 1250cc read your rule book for the class rules. People in Brisbane here are laughing.

[850cc racer]

Hi Derek, I can confirm 110% the boat has done 75mph with that motor on it. This thread is over 2 years old. i dont see why people are laughing? im only stating what it has done.

I later did 78mph when i first put the mod 50 on the boat.

[Steves Jem]

Hi Derek, I can confirm 110% the boat has done 75mph with that motor on it. This thread is over 2 years old. i dont see why people are laughing? im only stating what it has done.

I later did 78mph when i first put the mod 50 on the boat.

Hi 850 racer. The 1250 cc mono record was set by me with a speed of 81.33mph with a stock SST 60 OMC swinging a very thin 25inch prop with the motor height right on the temperature limit and cooled down at the end of each run. The boat is identical to yours. I beleive that this speed can be bettered as I had a one way speed of arround 85 mph. In 1980 the 1000 cc mono record was set by me with a FT 19s on the original wooden version at a speed of 82.33
mph.The FT19s was latter banned from competition as it was considered to not be a stock outboard. New records were called for and set with stock engines. I changed to a 75 hp Hustler and in 1988 set the1250 cc mono record at 76.88 mph with a 25 inch prop with the motor height on the temperatur limit and then overheated at the finish of the record attempt. As your motor is modified the speeds you state are obtainable but is all dependant on the diameter of your prop as those tha I ran were extremly thinned and less than 12 inch diameter. My kilo speeds were around 4 to 5 mph better than my circuit speeds due to a different setup and being able to swing the 25 inch prop. From memorary I think that the best revs by the stock 75 Hustler was 6400 - 6500. Are you still 850 cc racing.
Regards
Stephen Medaris

[Fast Fred]

the straight in Mod 50 made more power than the ft19s, it is a better moda

[Steves Jem]

Fast Fred. Yes these would be faster than the FT19S but would not have been allowed in Australia as the class in which the FT19S raced were stock motor class. The SST 60 that I raced was slightly slower than the FT19S. With a finger ported 920 OMC with a 31M straight front and dual carbs the mono was achieving speeds in the low 90mph which was a lot of fun. This modified 920cc motor was unreliable and prone to seizing No 1 piston due to airpockets around that cylinder. A teltail out of the thermostat resolved this. Also the heads were prone to cracking if shaved too much.
Regards
Stephen

[pdt]

this 920 engine is this the oval port engine ? the one made between 93 and 2004 ?
or an older engine ?

.

[Fast Fred]

bridge port makes a bigger overall Exhaust port, oval port is for a round power band and can not meet the over all size of a bridge port exhaust window. i have made good power with oval, but never as much as a bridge. i some have heard that some are makin more power with oval, reminds me of some racers that would cover there prop at the races like it was all that, thay were vary fast, too fast, for the rules . it was never the prop, it was the three trick ilegal sleves that thay had put in, cuzz of there big time last name they never got called on it, thats racin,

[pdt]

bridge port have larger area than oval ?????????

omc claimed the oval port had more exhaust area than the bridged port version from new on the standard motors that anyone could just walk in and buy.
im not talking about specials or sst60 race engines.
have you ever worked out the area of an oval port 56cu in engine fred, ? I have not, I am only going by what OMC claimed when the oval port 56 ci came onto the market.
I think there might even be something about it in their sales brochure for 1995/6 ?
being oval makes it a touch harder to actually measure the area I suppose. I have never tried, but would be interesting to actually find out.

.

[Powerabout]

a piece of graph paper is a quick and dirty measure

[Fast Fred]

you can measure all you want, the fact remains true. you could have two oval ports in the same bore with a bridge. the shape of the oval port makes for a wider power band. as in smooth through the power curve not more power, more smooth. i'd take a sold molded 56er bridge port block, aka fishinmotor. a bunch of dudes got sucked in on that concealed prop, payed big bucks for a copy, they never went as fast. careful about what you think you know....

[pdt]

so what is the area of the bridge ports and the area of the oval ?

what would be the benefit of any engine maker going to the trouble and cost of re-tooling to put in oval ports ?

Its not just omc who have done this, a few others also done it, must be a reason for this.

.

[Fast Fred]

cheaper to make, you can incorporate the oval into the bridge by makin the top of the window ark to the bridge = oval bridge port.

[OUTBOARDER]

Do you know what Time Area and blow down are? Area by itself is a small slice of the pie.

I vote for the block you can not use in OPC SST-60

http://www.wptracing.com/sst-60

"Modified Package for Inflatable Racing: We can build a trick mod engine with a better block than you can use in SST 60. This would have the cylinder block ported along with finger ports. Head machined to a specific race compression ratio. Special reeds and intake work. Special pistons, and many other little race details. Hang on tight" "

[sharpeye Mike]

Hey Fred, wasn't there a bridge port mod. 50 shape the way you just describe?
Thanks, Mike

[Fast Fred]

all three Mod 50's are bridge port modas, the 19s had slanted bridges, so you could not oil them. the solid mold 56er is the outlaw bridge port.

[Steves Jem]

Hi PDT.
It was the pre 1993 920 cc motor which was identical to the first SST60 engine.
Stephen

[pdt]

what is the height and width of the exhaust ports on the bridge port engine ?
I will have to measure my oval spare block tomorrow as im sure its bigger, but you have worked on them so should know.
I am realy interested to know the differences now.

I do understand a bit about the port timming, but some of this is new to me that's why I am asking.
if you know the exact sizes outboard ,then please put them down here.
.
.

[sharpeye Mike]

all three Mod 50's are bridge port modas, the 19s had slanted bridges, so you could not oil them. the solid mold 56er is the outlaw bridge port.

Solid mold 56er? got one of those but not sure what to do with the mods yet, it's going on short mid. and nitro gear case, pro 50 trim but I do know I want to keep the comp. at 150 to 160 lbs. The gas here in Canada sucks, I found 94 oc. but it has ethanol.
Mike

[pdt]

thanks for that steve
so what the difference with the later block ?
apart from being cast by a different means i.e lost foam, its still 920cc, ?

. I am asking because I don't know,

it seems like what I have been told about these is obviously bs if all these things are turning out to be so very different.:confused:

if you don't ask you don't know, so that's why I am asking about these things.
the port size I am a bit confused about as I have a spare oval port engine with what seems to be huge exhaust ports !!!!

.

[Tim Kurcz]

what is the height and width of the exhaust ports on the bridge port engine ?
I will have to measure my oval spare block tomorrow as im sure its bigger, but you have worked on them so should know.
I am realy interested to know the differences now.

I do understand a bit about the port timming, but some of this is new to me that's why I am asking.
if you know the exact sizes outboard ,then please put them down here.
.
.

Suggested reading is Gordon Jennings "Two stroke tuners handbook" where port-time-angle equations will help you understand one aspect of 2-stroke power delivery.

Specific to the topic at hand, manufaturers eliminated bridges because when overheated they expand inward and scuff pistons. As Fred points out, a common means of reducing the problem is oiling the bridge through drilled ports in the piston skirt. The factory method was to eliminate the bridge entirely, thus eliminating interference problems.

While reading Jennings, take time to study maximum port width as a function of bore diameter (there is a formula). I've successfully removed bridges from OMC Permold blocks and made more power the result of larger port openings with less restriction. Take care not to widen ports further as ring drop will be induced: Bridge supports rings.

Regardless, there are two major downsides to the OMC 56: Lack of sufficient cylinder cooling, and too long inter-cylinder merges. The Mod-50 and all late-model triple use shortest possible merges. Improving the exhaust would make more power than all the porting in the world.

Good luck with your project!

Tim

[pdt]

yes I have a copy of the 2 stroke tuners handbook. a member here sent it to me.

So what stops the so called oval port engines exhaust ports being enlarged (up or down)and the radius made better ? is there a reason this cannot be done to good effect.


what exactly is inter cylinder merges ? (sorry to ask but its another usa thing we have never heard of) probably know it when told what it is in uk English ha ha .

.

[Powerabout]

Just a thought...
fastest outboard ever, a bridgeport
fastest F3 49ci 31M also bridgeport
coincidence
OR
is that just a red herring as they have proper exhaust systems???

[Tim Kurcz]

yes I have a copy of the 2 stroke tuners handbook. a member here sent it to me.

So what stops the so called oval port engines exhaust ports being enlarged (up or down)and the radius made better ? is there a reason this cannot be done to good effect.


what exactly is inter cylinder merges ? (sorry to ask but its another usa thing we have never heard of) probably know it when told what it is in uk English ha ha .

.


A stated previously, port width is limited by the geometric formula precluding ring drop. If you want to be wild, try going beyond formula some time. Be sure to buy another block and pistons; you'll need them in 5 or so hours.

OMC 56 blocks have cast-in exhaust ducting that merges 5-8 inches downstream (depending in cylinder) of the ports for best low & mid torque. Tuning for best top end demands closest possible merges, hence the stunning performance of the Mod-50's.

Tim

[Fast Fred]

you can mill the exhaust on the 56er and fix it. set it up like a Mod50, it's been done.

150psi or 28cc head chamber is about the limit of pump gas.

time to go fix some boats

[Tim Kurcz]

you can mill the exhaust on the 56er and fix it. set it up like a Mod50, it's been done.

150psi or 28cc head chamber is about the limit of pump gas.

time to go fix some boats

Correcting interconnects is not as easy as milling the passages. To do it right, a casting needs to be made and it must be gasketed and attached securely with very limited space for fastener support. The fact it has been done does not mean it's been done right, or effectively. A big problem is connecting then routing back to the center outlet - a very tight space with sharp turns. A customer asked me to do it right but was not willing to spend the $$$ needed. Can post pics of the milled-away block, the operation breaks through water jackets and not pretty.

Fred and I generally agree on compression limits, but you need to realize that effective pulse tuning increases cylinder pressure dramatically. Some of my best motors deliver only 120 PSI cranking. This is deceiving because the exhaust ports are a mile high: Top end compression is a function of the top edge of your exhaust port. Because pistons/blocks are expensive to fix, and the season is short, I recommend 100LL avgas with minimum 16:1 oil regardless.

[pdt]

Yes the triple I have is restricted as far as doing anything with the exhaust housing for sure.
its not like the older type that could come off and be given a different exhaust manifold.

the 120 psi really does surprise me, if mine was 120 I would dump it....I have 148..149 ..148.
somewhere on here iwas told I need to get to atleast 165 psi and that maybe getting rid of the small reliefs could give me 10psi to help me raise it up a touch.

im finding it all very confusing , but great reading

[Fast Fred]

done at the factory, the way i did it was to mill it off, put it in the freezer, tig on it , back to the freezer, more tig, then mill the welds then cap it.

i don't think he is goin to change the exhaust so he would be ok with the fuel said at that comp spec.

good stuff:cool:

[Fast Fred]

cool, seem gots the right people lookin in hear maybe some more ausome notes

[ima75man]

fred, clear out a spot for me.

[Tim Kurcz]

Yes the triple I have is restricted as far as doing anything with the exhaust housing for sure.
its not like the older type that could come off and be given a different exhaust manifold.

the 120 psi really does surprise me, if mine was 120 I would dump it....I have 148..149 ..148.
somewhere on here iwas told I need to get to atleast 165 psi and that maybe getting rid of the small reliefs could give me 10psi to help me raise it up a touch.

im finding it all very confusing , but great reading


The only way you can get to 150 PSI+ is with low porting and a factory head milled .120" or so. A custom head with tiny pockets is needed to make up for high porting. The reason is compression is not generated until the exhaust port closes. So, the higher the porting, the lower the top end compression reading.

To confuse matters further, physics and architecture conflict in every engine. Consider that less swept volume (tall porting) combined with tiny combustion chambers means less air/fuel mixture available for combustion. Less air/fuel mix limits available power production.

Get it now?

[Powerabout]

what we need is a 3 cyl with bolt on exhaust and its made from the 45 stuff so longer rods and more stroke

[pdt]

The only way you can get to 150 PSI+ is with low porting and a factory head milled .120" or so
do you mean can only get 150+ psi on a worked on engine, or do mean 150 + is not possible on an engine like mine, the later 56ci oval ?

and 100 avgas over here is mental price if you can even get it without a civil aviation licence to get to the pumps at air field.

[Tim Kurcz]

The only way you can get to 150 PSI+ is with low porting and a factory head milled .120" or so
do you mean can only get 150+ psi on a worked on engine, or do mean 150 + is not possible on an engine like mine, the later 56ci oval ?

and 100 avgas over here is mental price if you can even get it without a civil aviation licence to get to the pumps at air field.


Port shape with or without bridges doesn't matter; upper timing edge and combustion chamber volume determine effective compression ratio. Regardless of ratio, you need to tune for the best available octane. E85 or other alcohol modified fuels are good for octane and cooling. The downside is it must be flushed from carbs every time you're done.

PS 100LL here is about $6 US/Gallon.

Tim

[Tim Kurcz]

The engine you ask for is readily available at BRP dealers........ The Etec 90.

[champ20B]

you can mill the exhaust on the 56er and fix it. set it up like a Mod50, it's been done.

150psi or 28cc head chamber is about the limit of pump gas.

time to go fix some boats

I'm not trying to change the conversation, but I am wondering what any opinion would be on what I have. My yamato 80 is 145psi exactly on both cylinders. Compression gauges can be a bit different though by a pound or so as Rick Montoya told me. But as far as pump gas goes, My 6NHR Champion Hotrod is reading 161psi on the top and 165psi on the bottom. It is an old 20cid racer. is this something I need to look at, as far as running pump gas? It is all completely stock with a carter carb. It doesn't look like it was used for alchohol at all. Any comment about this would be appreciated so I don't damage a piston or two. THANKS!

[Fast Fred]

if it was handed to me to fire it up, i'd check the mix,see what the factory wanted,and use LL100at the factory mix to fire it in the test tank, once i had her bumpin, i'd check temp then the timin setup, see if it swings or stiff arm, after a check for excessive timin , all being good to there i'd make a Pull, see if she is lazy in the curve, if felt that she was i'd cut the LL100 to 50% and 50% regular gas then, make Pull. i may only cut in 25% reg gas, i'd have to see and feel it to know for sure.... gots to run...

[sharpeye Mike]

Hey Fast, funny thing happen to me last year, I threw some 87 oc. by accident in my 75 Stinger with 150 lbs. comp. She actually ran faster.