Performance Improvements possible with newer 4 stroke outboards

[Hounddog]

Up here the new generation of racers are not interested it the old school 2 stroke motors. They would like to use their lap top and reprogram their motor same as they do with their cars. They don't mine throwing lots on money into their modifications. There is a very good supply of rebuildable 4 stroke outboards on the market for them to work with. The problem is there is limited information on what can be done to improve the performance or any OEM or aftermarket parts. Maybe there is not enough market for companies to spend the R&D money necessary to develop the products. Years ago the same could be said about the small Honda cars.
To-day that is a BIG business.
We need find ways to get these new people racing. Are you seeing the same thing in your area?
Any suggestions?

[Ron Hill]

I spent Saturday going over spec sheets "PAWING OVER" A Mercury four stroke head. Simon Motor Sports in San Diego has figured out how to, I think the word is "Flash" the computer, so they can disconnect the revlimiter.

But the motors will still only turn 6,500 RPM's.

My "PROJECT" is "Top Secret" right now, but I will tell you there are many areas that the Mercury 40-60 four stroke can be improved.

I will be "Up Front" with you. The head looks like the flow may well be restricted on purpose. (Need to sell better running motors in the future, you know built in obsolescence).

The value springs may be too weak, and allow the values to "FLOAT".

The exhaust area of the exhaust ports appears to be "Squeezed" down, this me be for pollution reasons, or just planned horse power control.

"My People" are going to run the numbers, and figure out what the cam is and what they think the cam should be.

At this time, I have no plans to market anything for these motors. I am working as a "MIDDLE MAN" with some people than want improved performance and they have the financial backing needed for some development work.

I just wish for you guys in Canada, would look at Texas, Tri Hull's roll cages. Or go to 660 drags. Todd Bucknell's accident, last summer, was not got for boat racing!

I have no "FACTS" other than hear say, but It appears the NEW Tohatsu four stroke has some real power. I have 18 pitch props running on 30 HP Tohatsu four strokes and hitting the rev limiter.

[Hounddog]

Thanks Ron, yes we are alike! We both want to promote our sport. Our Drag group here is finalizing 2 additional 660 Drag races this summer and T Class is included. Any accident where someone is hurt is not good for our sport. There were a number factors in Todd's accident. The weather was one of them. It was BAD! The T racers wanted to race even though the other classes could not. There were a lot of fans at that race and the racers did not want the cancel Sunday's complete race day. I am not sure if a cage would have helped in this accident because the impact was thru the bottom of the hull and not the side.
For the last couple of years I have been working on a Critchfield rework. I have the strong box going all the way to the nose. The boat is carbon fiber construction and now after Todd's accident I am adding another layer to the front section. Two of my other T boats already have cells.

[Tiller guy]

I spent Saturday going over spec sheets "PAWING OVER" A mercury four stroke head. Simon Motor Sports in San Diego has figured out how to, I think the word is "Flash" the computer, so they can disconnect the revlimiter.

But the motors will still only turn 6,500 RPM's.

My "PROJECT" is "Top Secret" right now, but I will tell you there are many areas that the Mercury 40-60 four stroke can be improved.

I will be "Up Front" with you. The head looks like the flow may well be restricted on purpose. (Need to sell better running motors in the future, you know built in obsolescents).

The value springs may be too weak, and allow the values to "FLOAT".

The exhaust area of the exhaust ports appears to be "Squeezed" down, this me be for pollution reasons, or just planned horse power control.

"My People" are going to run the numbers, and figure out what the cam is and what they think the cam should be.

At this time, I have no plans to market anything for these motors. I am working as a "MIDDLE MAN" with some people than want improved performance and they have the financial backing needed for some development work.

I just wish for you guys in Canada, would look at Texas, Tri Hull's roll cages. Or go to 660 drags. Todd Bucknell's accident, last summer, was not got for boat racing!

I have no "FACTS" other than hear say, but It appears the NEW Tohatsu four stroke has some real power. I have 18 pitch props running on 30 HP Tohatsu four strokes and hitting the rev limiter.

I was researching the merc inline 3 cylinders and found info suggesting they have valve float beyond the factory recommended rpm's.

[88workcar]

I have ported several Yamaha and Merc 4 stroke heads, we have had decent success so far. The valve springs are weak, the ECU mod would be awesome

[Ron Hill]

I have heard, that Simon Motor Sports can "FLASH" the ECU on Mercury 40-60 HP. http://www.simonmotorsports.com/ I'll admit, I don't know what an ECU is. I do know what a rev limiter is.

I've talked to them on the phone, super polite and helpful, though I didn't have very clear questions.

[Fastjeff57]

Typically, valve springs are always an issue in running 4 strokes at high rpm. To hot rod one of these 4 stroke OBs, you'd need to install a higher performance cam, stiffer springs, and possibly lighter valve rain components. I suppose some cam manufacturer out there would develop and sell high performance cams for these things IF the demand was there.

Jeff

PS: Getting on plane with a 'hot cam' could be a problem here. It is for Go Fast boats with high speed propping.

[twzted]

Hate to revive an old thread, but anyone have any more info as far as performance is concerned on these 4 strokes? I have a merc formula race 60 15" and like to get it tuned by simon, Ron hill have you heard of anyone running one by now? what was the increase? Car worker how has the head work done for performance?

[Tiller guy]

I read somewhere that those motors can't handle high rpm's because of valve float. Fact or BS?

[twzted]

Not sure, I have heard 6500 rpm is safe any higher is asking for trouble with the valves. Ill be happy with 6500, they rev up to 6300 stock thats pretty high for a stock 4 stroke. Im hoping someone with more inside knowledge can chime in, id really like to tune it although they claim only 5-7 hp gain and from what i hear the engine at 6300 rpm pushes about 65-68 hp so that would put it into the 70+ hp range and id be happy with that. Its hard to find a new midrange power plant with a short shaft and good gear ratio anymore without piecing old stuff together. Thats why i bought the merc 4 stroke. theres small rapid crafts running them at 65 mph so its respectable, just turn key and go, great on fuel too. In the uk they race these on boats 16' 1200+ lbs 60+ mph with merc cleavers. some actually run Hills props too.

[Powerabout]

I heard Merc tried to mod that 4s60hp lump on the European F4, it kept blowing up so it went back to stock?
Goes into gardian mode just getting off the dock and maybe down the straight, dont know if they fixed that?

[Powerabout]

Up here the new generation of racers are not interested it the old school 2 stroke motors. They would like to use their lap top and reprogram their motor same as they do with their cars. They don't mine throwing lots on money into their modifications. There is a very good supply of rebuildable 4 stroke outboards on the market for them to work with. The problem is there is limited information on what can be done to improve the performance or any OEM or aftermarket parts. Maybe there is not enough market for companies to spend the R&D money necessary to develop the products. Years ago the same could be said about the small Honda cars.
To-day that is a BIG business.
We need find ways to get these new people racing. Are you seeing the same thing in your area?
Any suggestions?

If they want to spend money get them to make EFI kits for old 2 strokes
create a new EFI controller for etec injectors now ya talking

[Tiller guy]

I'm sure someone knows how to work those heads. It would be a fun project to play with.

[Ron Hill]

I'm sure someone knows how to work those heads. It would be a fun project to play with.

I think his name is Jerry. Been grinding cams since the Kenny Harmon days. Kenny welded cam's lobs on 250 Honda Motorcycles and then re ground them. Lit those 250's up. Jerry regrinds the cams and sells valve springs. We gained 10% with this cam on a 40 HP.
Flashing the computer helps ZERO UNLESS THE VALVE SPRING ALLOW HIGH RPM'S.

[Powerabout]

I think his name is Jerry. Been grinding cams since the Kenny Harmon days. Kenny welded cam's lobs on 250 Honda Motorcycles and then re ground them. Lit those 250's up. Jerry regrinds the cams and sells valve springs. We gained 10% with this cam on a 40 HP.
Flasing the computer helps ZERO UNLESS THE VALVE SPRING ALLOW HIGH RPM'S.
but you had gears....

[Powerabout]

I'm sure someone knows how to work those heads. It would be a fun project to play with.
I think the issue might be most of the engines are highly optimized to do the job they were designed for hence as light as possible.
Its not a LS3 where GM knows they will be getting a hard time.
IMHO you might find there are many weak links in the chain if you make more power and revs and those parts are going to cost way more than the old 2 stroke when it goes bang.

[Ron Hill]

The problem with 2 strokes, right now, there are no new one in America. And they haven't made any for 15 years or so.

The people I deal with race hard in drag racing with their two strokes, but they do blow engines up and parts are getting harder to find.

Guy buy new four strokes, put them on a boat that went 50 MPH and the new Four Strokes go 42 MPH. With the help of the Signature Propellers we have been making, we have the speed up 12 MPH.

Looking the heads over, figuring compression ratios, porting the heads, grinding the cams, changing the valve springs, we will gain power!

For how long? That is the question!

Prop looks somewhat like this, but this is not the "HOT PROP" for 50 HP 4 strokes.

[twzted]

The problem with 2 strokes, right now, there are no new one in America. And they haven't made any for 15 years or so.

The people I deal with race hard in drag racing with their two strokes, but they do blow engines up and parts are getting harder to find.

Guy buy new four strokes, put them on a boat that went 50 MPH and the new Four Strokes go 42 MPH. With the help of the Signature Propellers we have been making, we have the speed up 12 MPH.

Looking the heads over, figuring compression ratios, porting the heads, grinding the cams, changing the valve springs, we will gain power!

For how long? That is the question!

Prop looks somewhat like this, but this is not the "HOT PROP" for 50 HP 4 strokes.



Hi ron, Are the semi cleavers performing best on the merc 4 strokes? If Evinrude would release a mid hp with a short shaft and a good lower unit that would be great, but dosent look like that will happen, we can only hope mercury makes some smaller lighter more powerfull 4 strokes, the 300r seems to be pretty awesome, just put some of that tech into the smaller engines and there may be some hope.

[Ron Hill]

Go with a winner and Mercury and Yamaha are the winners....well Tohatsu has some "hot" 40-50 HP four strokes with that 2.23 gear ratio...But with Evinrude, let's just say "If Evinrude"....

Look on Facebook for Kent Foreman, Foreman Marine. He seems to win all the races.

[Powerabout]

How about the sound, a modded v8 merc will sound good, but the rest, yuk!
Look what happened in FIA F1 when they dropped the v8
Nascar with a v6?

[oledawg]

Aside from using a laptop to modify fuel delivery & timing curves on 4-strokes, mechanical mods would be required. The motors with removable heads can increase compression by milling head surface. However, to change the equivalent of 2-stroke port timing, requires an after market camshaft. No one will engage in doing so because the volume is too small to justify start up costs. As Don has suggested, without a larger market for after market components, that will never happen.

I believe the only road to 4-stroke success in racing is to have the rev limiters removed or re flashed, to allow lower pitch props to wind up higher than the stock limiter will allow. This will give better acceleration without sacrificing top end speeds. I know in T-750, Tom'
s 60hp Mercury would kick our butts if he could remove limiter and run lower pitch props. When Tom gets good top end numbers, his acceleration suffers and vise versa. The only other solution to racing 4-strokes is to only allow them in the class, based upon displacement and/or horsepower.

Just my two cents.

[25XS]

The problem with 2 strokes, right now, there are no new one in America. And they haven't made any for 15 years or so.

Huh? Evinrude's entire lineup from 15hp to 150hp is the two stroke E-tec engine...
Tohatsu's TLDI is available in 40/50/90 hp and these are all still very close in weight to their old carbureted engines.
Mercury Marine's last two stroke currently offered is the Optimax 200hp jet drive (for recreational squirt boats) but that means they still make the 2.5L powerheads.

[PPRINT]

WebCam Racing Cams can modify factory camshafts to a certain degree. That would be my first goto if hp gains were wanting to be had on a 4-stroke.

Webcamshafts.com

RobT

Sent from my SAMSUNG-SM-G900A using Tapatalk

[Powerabout]

Huh? Evinrude's entire lineup from 15hp to 150hp is the two stroke E-tec engine...
Tohatsu's TLDI is available in 40/50/90 hp and these are all still very close in weight to their old carbureted engines.
Mercury Marine's last two stroke currently offered is the Optimax 200hp jet drive (for recreational squirt boats) but that means they still make the 2.5L powerheads.

Merc still building small engine carby 2 strokes but not for sale in the USA

[Ron Hill]

but you had gears....

When my dad worked my props, my best props were "Shifters". They crowd in Seattle have figured this out in kneel down racing.

[Hounddog]

T-750, Tom's 60hp Mercury would kick our butts if he could remove limiter and run lower pitch props. When Tom gets good top end numbers, his acceleration suffers and vise versa. The only other solution to racing 4-strokes is to only allow them in the class, based upon displacement and/or horsepower.

I still think we can help Tom and other current and new racers in T750 class if we increased the minimum weight from 500 lbs to 625 lbs. Unlike our T850 class which has a surplus of horsepower that makes up for boats being 150 lbs. over weight, our T750 over weight boats have much less exceleration and that hurts lap times. If you had a new composite Critchfield at 225 lbs, an OMC twin at 200 lbs, gear at 25 lbs., and a average weight driver at 175 lbs you are at 625 lbs That should be the minimum weight!!

[oledawg]

I agree that the minimum T-750 weight is to light. Most boats weigh 250-260 lbs. or more. ( The Rossiter Critch is 225 lbs. w/o the 16 lb. cowl.) The rigging weighs 75-80 lbs. I know since, I just rigged our new T-750. Throw in 20 lbs. of fuel and a 200lb. twin two stroke and you have 550lbs. without the driver. That is already close to the current class legal weight. That all but eliminates any driver that weighs more than 150lbs. Our lightest driver is 140lbs. and our heaviest is 230lbs. That is a 100lb. weight disadvantage. That's tough to deal with in T-850 much less T-750. If T-850 is 725 lbs. than why is T-750, 594 lbs. The motors are only 30lbs. more in T-850. Why roughly 125lbs. less in T-750??? I think T-750 should be 675 lbs. & T-850, 800 lbs. This would attract racers that are bigger guys or gals. Why exclude a large number of potential new racers in our T-750 class.

[Hounddog]

I agree why is T-750, 594 lbs. The motors are only 30lbs. more in T-850. Why roughly 125lbs. less in T-750??? I think T-750 should be 675 lbs. & T-850, 800 lbs. This would attract racers that are bigger guys or gals. Why exclude a large number of potential new racers in our T-750 class.

T Class is a UIM World Class...the weights for both T750 and T850 came from those rules. APBA similar classes were DE for T750 and EP for T850...I am not sure about the DE weight but APBA EP was 850 lbs. With 3 cylinder drag in 2019 the T guys may want a heavier weight..It would be a class decision. Remember OPBRA is looking to revise T850 for the 2020 season.

[twzted]

I still think we can help Tom and other current and new racers in T750 class if we increased the minimum weight from 500 lbs to 625 lbs. Unlike our T850 class which has a surplus of horsepower that makes up for boats being 150 lbs. over weight, our T750 over weight boats have much less exceleration and that hurts lap times. If you had a new composite Critchfield at 225 lbs, an OMC twin at 200 lbs, gear at 25 lbs., and a average weight driver at 175 lbs you are at 625 lbs That should be the minimum weight!!

Tom is a great guy, he gave me alot of info on the Merc formula race, I'm finishing up my boat soon it's a 13' bullet, I'm not racing but I want the most I can get out of it. It's heavy at 400lb bare hull but I rebut it for offshore durability and all composite.

[Ron Hill]

One of my customers claims a re ground cam helped his Honda, noticeably. He has a 100 hours on the cam.

From second hand information via Mercury Marine, all their smaller 4 Stokes are tamed way down, so they can sell you newer, more powerful ones later.

I do know the early Yamaha 4 Stokes were "Weak Sucks". BUT THE NEWER ONES SEEM TO HAVE SOME LOW AND AND TOP IN GRUNT.

[twzted]

One of my customers claims a re ground cam helped his Honda, noticeably. He has a 100 hours on the cam.

From second hand information via Mercury Marine, all their smaller 4 Stokes are tamed way down, so they can sell you newer, more powerful ones later.

I do know the early Yamaha 4 Stokes were "Weak Sucks". BUT THE NEWER ONES SEEM TO HAVE SOME LOW AND AND TOP IN GRUNT.


If there was a package I'd buy it but once you start messing with Cam duration and what not a special tune would need to be made I would think, Simon performance does have a tune for the Merc 60, boosts up low mid range power pretty good, and supposedly adds about 5-7 hp where it supposedly makes around ,68 at 6300 rpm, that puts it over 70.i have been trying to find someone who has used their tune to get a real world answer. It's 650$ and for it to do nothing would be a waste and could buy more props. I have a merry 12x22 cleaver Wich I believe will be a bit big for my boat but if it's tuned it may work perfectly.

[Ron Hill]

If there was a package I'd buy it but once you start messing with Cam duration and what not a special tune would need to be made I would think, Simon performance does have a tune for the Merc 60, boosts up low mid range power pretty good, and supposedly adds about 5-7 hp where it supposedly makes around ,68 at 6300 rpm, that puts it over 70.i have been trying to find someone who has used their tune to get a real world answer. It's 650$ and for it to do nothing would be a waste and could buy more props. I have a merry 12x22 cleaver Which I believe will be a bit big for my boat but if it's tuned it may work perfectly.

I have been told that them motors still won't rev, and the valve spring are too weak. With a re ground cam and heavy duty spring, "FLASHING" the computer helped a lot.

[twzted]

I have been told that them motors still won't rev, and the valve spring are too weak. With a re ground cam and heavy duty spring, "FLASHING" the computer helped a lot.


Ron, have you herd of anyone that used Simons tune and said it was worth it? I would like to try one of your semi cleavers once my 13' bullet boat is done, will try my 12x22 merc cleaver first and get a base line but I anticipate its a little to big.

[Hounddog]

T Class is a UIM World Class...the weights for both T750 and T850 came from those rules. APBA similar classes were DE for T750 and EP for T850...I am not sure about the DE weight but APBA EP was 850 lbs. With 3 cylinder drag in 2019 the T guys may want a heavier weight..It would be a class decision. Remember OPBRA is looking to revise T850 for the 2020 season.

I just noticed on the TORC......Toronto Outboard Race Club..site that the link to the rule book is a link to the 2019 UIM Rule Book....T Class starts on page 194. There is no change in the T750 weight. The GT classes for the New motors are much heavier and are horsepower based not displacement based as the two stroke classes. Our new composite Critchfields weigh 225 lbs without the cowl, we will see the new 2019 redesign Deltas this race season and they could be lighter and quicker than the Critchfield or Allison. One reason OPBRA is looking at reducing the horsepower in T850 is the boats are having turning problems in the corners due to the increased top end speeds on the straights.
They may want to go back to the original spec rules and eliminate the altered 56 fishing motor. Under the original rules you could run a UIM spec 49 OMC or 70CES, an APBA spec 59 cubic inch Mercury, an APBA spec SST 60 with the larger cc 160 compression head or a blueprinted stock 56 fishing motor with the 160 compression head. All of these motors were competitive, some had better acceleration while the OMC 49 and SST 60 had a bit more top end. Made for multiple winners and super racing for the fans.
Simple solution for the OMC 56’s......must run 31.5 cc head regardless of resulting compression and 73D maximum jet size.. That will slow down the altered motors and is easy to check at inspection.

[twzted]

I just noticed on the TORC......Toronto Outboard Race Club..site that the link to the rule book is a link to the 2019 UIM Rule Book....T Class starts on page 194. There is no change in the T750 weight. The GT classes for the New motors are much heavier and are horsepower based not displacement based as the two stroke classes. Our new composite Critchfields weigh 225 lbs without the cowl, we will see the new 2019 redesign Deltas this race season and they could be lighter and quicker than the Critchfield or Allison. One reason OPBAR is looking at reducing the horsepower in T850 is the boats are having turning problems in the corners due to the increased top end speeds on the straights.
They may want to go back to the original spec rules and eliminate the altered 56 fishing motor. Under the original rules you could run a UIM spec 49 OMC or 70CES, an APBA spec 59 cubic inch Mercury, an APBA spec SST 60 with the larger cc 160 compression head or a blueprinted stock 56 fishing motor with the 160 compression head. All of these motors were competitive, some had better acceleration while the OMC 49 and SST 60 had a bit more top end. Made for multiple winners and super racing for the fans.
Simple solution for the OMC 56’s......must run 31.5 cc head regardless or resulting compression. That will slow down the altered motors and is easy to check at inspection.

Hounddog, how does Toms 4stroke Merc perform? I'm sure it dosent accelerate as quick as the two stroke and being stock how does it compare? Is he running in the modified class of 2 strokes with it or is he running with stock 60 2 strokes? I heard he hit 65 mph with a prop of a nother boat that couldn't run 65 with it. I only ask because I have one and will be putting it on a 13' bullet curious your opinion. I know they are super reliable and great on fuel.

[Powerabout]

I just noticed on the TORC......Toronto Outboard Race Club..site that the link to the rule book is a link to the 2019 UIM Rule Book....T Class starts on page 194. There is no change in the T750 weight. The GT classes for the New motors are much heavier and are horsepower based not displacement based as the two stroke classes. Our new composite Critchfields weigh 225 lbs without the cowl, we will see the new 2019 redesign Deltas this race season and they could be lighter and quicker than the Critchfield or Allison. One reason OPBAR is looking at reducing the horsepower in T850 is the boats are having turning problems in the corners due to the increased top end speeds on the straights.
They may want to go back to the original spec rules and eliminate the altered 56 fishing motor. Under the original rules you could run a UIM spec 49 OMC or 70CES, an APBA spec 59 cubic inch Mercury, an APBA spec SST 60 with the larger cc 160 compression head or a blueprinted stock 56 fishing motor with the 160 compression head. All of these motors were competitive, some had better acceleration while the OMC 49 and SST 60 had a bit more top end. Made for multiple winners and super racing for the fans.
Simple solution for the OMC 56’s......must run 31.5 cc head regardless of resulting compression and 73D maximum jet size.. That will slow down the altered motors and is easy to check at inspection.

propshaft height is another way to slow boats down and helps safety re spins

[Hounddog]

Hounddog, how does Toms 4stroke Merc perform? I'm sure it dosent accelerate as quick as the two stroke and being stock how does it compare? Is he running in the modified class of 2 strokes with it or is he running with stock 60 2 strokes? I heard he hit 65 mph with a prop of a nother boat that couldn't run 65 with it. I only ask because I have one and will be putting it on a 13' bullet curious your opinion. I know they are super reliable and great on fuel.

There is a big difference between running in a oval boat race and seeing the best top speed. The oval boat race is about the fastest lap time not the fastest speed. Tom runs against stock 2 stroke motors. The top runners in the class have good acceleration and hit over 61 mph on the straight. Tom can match their acceleration with a 19 pitch prop. Problem is they have the extra mile or two top end. When Tom runs his 65 mph prop they have superior acceleration and he cannot catch them.
To be Honest Tom does not get the best clock starts and is usually not the first boat to the first turn. When he has, he has been tough to catch. I think with a 21 pitch and a good start he can win.

[Hounddog]

propshaft height is another way to slow boats down and helps safety re spins
We currently have a prop shaft UIM rule.....basically it must be below the bottom of the boat and we allow nose cones but not low water pick up nose cones or remote transom water pick-ups. We put the nose cone rule in because many T boat owners up here ran SST 60 lower units. At first in 2006 we thought the SST 60 lower units would be an advantage over the nitro case. This was race proven to be false, the nitro case is the faster case on a T boat. The Yamaha small case is even better and the Mercury case even better provided the carrier did not come out. APBA VP75 run the large case with the prop shaft 5 inches?? below the boat plus a much heavier minimum weight. That class has really grown and has many good looking expensive boats racing....and it is much slower compared to our T classes. A few years a go we ran a short shaft big foot 49 with the 725 lb T850 minimum weight in T750. The actual boat and driver used was well over 850 lbs. The boat was a top 3 runner back then. We dropped the idea after one season because it was obvious that had the boat been close to the 725 lb weight, it would dominate.
Maybe??? When T850 is reviewed for 2020 we could revisit this idea with a minimum weight at 850 lbs.

[twzted]

There is a big difference between running in a oval boat race and seeing the best top speed. The oval boat race is about the fastest lap time not the fastest speed. Tom runs against stock 2 stroke motors. The top runners in the class have good acceleration and hit over 61 mph on the straight. Tom can match their acceleration with a 19 pitch prop. Problem is they have the extra mile or two top end. When Tom runs his 65 mph prop they have superior acceleration and he cannot catch them.
To be Honest Tom does not get the best clock starts and is usually not the first boat to the first turn. When he has, he has been tough to catch. I think with a 21 pitch and a good start he can win.

Yea i knew it was a higher pitched prop not best for oval racing, im not racing but i do long runs down in the Florida keys 100+ miles ( all straight ) sold my supercharged waverunner and am building this boat, i plan to go with all the skis i used to ride with so i want to try and keep up. I have a 12x22 labbed Merc cleaver for it. Like i said i dont plan on racing but want the best performance i can get out if it, I was really just seeing your thought on the engine in perticular performance wise. whats the difference between the T750 boats and the 850? i know most are 70+ hp but whats the speed difference like?

[Hounddog]

Yea i knew it was a higher pitched prop not best for oval racing, im not racing but i do long runs down in the Florida keys 100+ miles ( all straight ) sold my supercharged waverunner and am building this boat, i plan to go with all the skis i used to ride with so i want to try and keep up. I have a 12x22 labbed Merc cleaver for it. Like i said i dont plan on racing but want the best performance i can get out if it, I was really just seeing your thought on the engine in perticular performance wise. whats the difference between the T750 boats and the 850? i know most are 70+ hp but whats the speed difference like?
The T750 boats are 55 to 67 hp. The T850 altered 56 OMC ‘s are 100 hp plus. Speed wise the T750 record is over 65 mph. Our best T850 recorded speed is 80 mph while the UIM T850 record is 68 mph. Overall all the feedback I get about the 60 is positive. Interesting that you have a 12 x 22 Mercury prop. The original model of that prop is liked by many T guys. With your boat you may find it is too much prop. I would not be surprised if an 11.5 x 18 works better. One last comment....I had a fellow running a 1998 59 cubic inch 2 stroke Mercury switch to the 4 stroke. The 2 stroke acceleration was better, but the 4 stroke was only 1 mile an hour slower. So for a non race application...equal!!

[twzted]

The T750 boats are 55 to 67 hp. The T850 altered 56 OMC ‘s are 100 hp plus. Speed wise the T750 record is over 65 mph. Our best T850 recorded speed is 80 mph while the UIM T850 record is 68 mph. Overall all the feedback I get about the 60 is positive. Interesting that you have a 12 x 22 Mercury prop. The original model of that prop is liked by many T guys. With your boat you may find it is too much prop. I would not be surprised if an 11.5 x 18 works better. One last comment....I had a fellow running a 1998 59 cubic inch 2 stroke Mercury switch to the 4 stroke. The 2 stroke acceleration was better, but the 4 stroke was only 1 mile an hour slower. So for a non race application...equal!!

Cool, yea i may need to drop some pitch and or diamiter but i know i could sell the 12x22 easily as they are very good on the f4s boats, i may try one of Mr Hills props if it dosent work or trade mine for another merc cleaver.

[Powerabout]

We currently have a prop shaft UIM rule.....basically it must be below the bottom of the boat and we allow nose cones but not low water pick up nose cones or remote transom water pick-ups. We put the nose cone rule in because many T boat owners up here ran SST 60 lower units. At first in 2006 we thought the SST 60 lower units would be an advantage over the nitro case. This was race proven to be false, the nitro case is the faster case on a T boat. The Yamaha small case is even better and the Mercury case even better provided the carrier did not come out. APBA VP75 run the large case with the prop shaft 5 inches?? below the boat plus a much heavier minimum weight. That class has really grown and has many good looking expensive boats racing....and it is much slower compared to our T classes. A few years a go we ran a short shaft big foot 49 with the 725 lb T850 minimum weight in T750. The actual boat and driver used was well over 850 lbs. The boat was a top 3 runner back then. We dropped the idea after one season because it was obvious that had the boat been close to the 725 lb weight, it would dominate.
Maybe??? When T850 is reviewed for 2020 we could revisit this idea with a minimum weight at 850 lbs.

Wow, large gearcase with propshaft just under and very low ratio was fast??
What caused that do you think, more diameter with low ratio would get you out of the corners I guess?
How many seconds in a lap for your typical course?
Would make a cheap class i thought, big case on a 15" with stock 49er

[Hounddog]

Wow, large gearcase with propshaft just under and very low ratio was fast??
What caused that do you think, more diameter with low ratio would get you out of the corners I guess?
How many seconds in a lap for your typical course?
Would make a cheap class i thought, big case on a 15" with stock 49er

We tried the 49-big foot-15 inch for several reasons. One was to compare the performance to the VP75 class which only allows long shaft motors. We had tried the long shaft version with a Checkmate a few years prior. T racers did not like the way the long shafts handle. The FE Class prior to 1975 ran big foot short shafts, so we were following that model. The test boat ran 57 to 58 mph with a 12.5 x 24 omc prop. Our course is approximately 1 mile at most sites....top T750 boats about 67 seconds....top T850 boats under 60 seconds. There is a big difference in lap times after lap 3....when we had 9 boats in a heat the water is rough! More prop diameter helps out of the turns in rough water. Another option we have tried on a lake runner is running the higher ratio 2 cylinder nitro on a 49. Works well and is less than half the cost a 3 cylinder nitro. I personally like this option better than the big foot.....same lower cost, but boat handles better and is 3 to 4 mph faster...low 60’s.

[Powerabout]

We tried the 49-big foot-15 inch for several reasons. One was to compare the performance to the VP75 class which only allows long shaft motors. We had tried the long shaft version with a Checkmate a few years prior. T racers did not like the way the long shafts handle. The FE Class prior to 1975 ran big foot short shafts, so we were following that model. The test boat ran 57 to 58 mph with a 12.5 x 24 omc prop. Our course is approximately 1 mile at most sites....top T750 boats about 67 seconds....top T850 boats under 60 seconds. There is a big difference in lap times after lap 3....when we had 9 boats in a heat the water is rough! More prop diameter helps out of the turns in rough water. Another option we have tried on a lake runner is running the higher ratio 2 cylinder nitro on a 49. Works well and is less than half the cost a 3 cylinder nitro. I personally like this option better than the big foot.....same lower cost, but boat handles better and is 3 to 4 mph faster...low 60’s.

thanks Hounddog
sounds like there are lots of options and sustainable/easy to find parts
I thought about a new mid for the 56 so it bolts up, 15" and solid mounts, go racing ( cut drive shaft)

[Hounddog]

thanks Hounddog
sounds like there are lots of options and sustainable/easy to find parts
I thought about a new mid for the 56 so it bolts up, 15" and solid mounts, go racing ( cut drive shaft)

Here in Ontario, Canada we have a shorter boating season and all fresh water so motors last longer and are in better condition compared to most areas. The 75 cent Canadian Dollar hurts when buying from the USA. With the above in mind I think a Hobby T Class would grow once we got a few boats racing. We need to take advantage of the good low cost motors available here and keep the spec rules simple and easy to understand.
HOBBY T CLASS
- V hull
- 850 lb minimum weight
- bone stock 3 cylinder 60 cubic inch maximum ..no custom parts!..Stock head and stock compression!
- no blueprinting
- MOTORS..choice of long or short shaft model
- OMC 49 small carb...choice of big or small lower unit
- Yamaha 52 no CES parts...choice of big or small lower unit
- Mercury 49, 52 or 59 bone stock
Should be a 55 to 62 mph class.
Current Other T rules would apply.

[Powerabout]

Here in Ontario, Canada we have a shorter boating season and all fresh water so motors last longer and are in better condition compared to most areas. The 75 cent Canadian Dollar hurts when buying from the USA. With the above in mind I think a Hobby T Class would grow once we got a few boats racing. We need to take advantage of the good low cost motors available here and keep the spec rules simple and easy to understand.
HOBBY T CLASS
- V hull
- 850 lb minimum weight
- bone stock 3 cylinder 60 cubic inch maximum ..no custom parts!..Stock head and stock compression!
- no blueprinting
- MOTORS..choice of long or short shaft model
- OMC 49 small carb...choice of big or small lower unit
- Yamaha 52 no CES parts...choice of big or small lower unit
- Mercury 49, 52 or 59 bone stock
Should be a 55 to 62 mph class.
Current Other T rules would apply.

solid mounts?
I have watched a few videos of that long shaft stock class and its a bit dodgy

[Hounddog]

solid mounts?
I have watched a few videos of that long shaft stock class and its a bit dodgy

Solid motor are part of the current T rules so Hobby Class could use them. The idea in Hobby Class is for the person who just wants to try T racing. They are not going to rebuild the motor, they will just buy a used cheap one and run it. T750 and T850 are very competitive classes where racers need to spend more. Hobby racers will use loaner props and safety gear. They will likely have less than $1500.00 invested. You will see experienced T racers and former champions run in this class. They want to grow the sport and are there to teach. We could see loaner complete outfits where newbie racers just sign up for an event. The low cost and availability of equipment make it possible!

[slowJEEP]

That Hobby, 750 and 850 sounds like a good time.

[Powerabout]

That Hobby, 750 and 850 sounds like a good time.

Racing any class with those engines always make a great class

[slowJEEP]

Merc 60 4S is just a smidge over 60ci though. 60.8 ish. Even though it's a turd in factory form, there are a few of us working to hop them up. Perhaps a 61 inch max would be better...

[Powerabout]

Merc 60 4S is just a smidge over 60ci though. 60.8 ish. Even though it's a turd in factory form, there are a few of us working to hop them up. Perhaps a 61 inch max would be better...

You can see why it went nowhere in the usa when a 45ci sst45 craps all over it

[slowJEEP]

Yep. Takes an expensive 4 stroke to out hp/ci a 2 stroke and the 60 merc is a far cry from high performance.

[Bateman]

I like mixing gas and hauling azz myself. I get tickled at my friends who think four strokes are more reliable.

[Flx]

Hi,

I am the guy with the boosted honda 50hp

Yes the camshaft made a hudge difference in the high rpm, i now keep getting the rev limiter at 6600rpm with 4 blade cleaver 10.5x18,

The engine is tweaked on the ignition by at least 3 degree of advance. This also make a hudge difference, let just say it is not a quiet honda anymore. Once you twist the gas, there just no lag, it will spin to the top.

Ive since bought a brand new boat, my next bet is a yamaha 70hp, these engine with a simple ecm reflash can gain 15hp, it would be even more with porting, camshaft and more compression.

The major problem i had with the honda is oil ingestion by the pcv tube at high rpm. It could be easy fixed with a catch can.

If you balance the engine i think it could run easy over 8k rpm. With headwork also !

Lundin marine can reflash any 4stroke and is located in norway. He is a king pin.
JBmecanical is located in australia. That guy live tune outboard.

[twzted]

Hi,

I am the guy with the boosted honda 50hp

Yes the camshaft made a hudge difference in the high rpm, i now keep getting the rev limiter at 6600rpm with 4 blade cleaver 10.5x18,

The engine is tweaked on the ignition by at least 3 degree of advance. This also make a hudge difference, let just say it is not a quiet honda anymore. Once you twist the gas, there just no lag, it will spin to the top.

Ive since bought a brand new boat, my next bet is a yamaha 70hp, these engine with a simple ecm reflash can gain 15hp, it would be even more with porting, camshaft and more compression.

The major problem i had with the honda is oil ingestion by the pcv tube at high rpm. It could be easy fixed with a catch can.

If you balance the engine i think it could run easy over 8k rpm. With headwork also !

Lundin marine can reflash any 4stroke and is located in norway. He is a king pin.
JBmecanical is located in australia. That guy live tune outboard.



The Yamaha 70 is the same powerhead at the Mercury 50-60hp Yamaha added their own touch.

[slowJEEP]

Where are you out of Flx?

[Flx]

I am located in canada quebec, excuse my poor english !

[Flx]

Yamaha f60 and f70 are infact same engine, beside the engine head,


The lower unit on the f60 is very interesting, with 1.85 gear ratio, a guy on facebook told me you could swap both.

My plan is to get a f70 with the f60 lower unit, and then get the ecm reflash.72765
72766
72767

[N hall91]

We raced the Mercury formula race motor for one season. It was loaned to us by Mercury Racing. It needed the gears from the two stroke motor. Other than that it was great.73148

[Flx]

What gear ratio did you use ?

[N hall91]

I think the stock ratio is 1.84 . That is what we used but the 60 two stroke uses the 1.63 ratio. The ecm in this motor has all the safety features removed except for the rev limiter.