Interest in new 3 cylinder drag rules..motor alterations and mixing manufacture parts

[Hounddog]

The first interest I have is building a 49 cubic inch out of the 3 cylinder 40/50 hp Yamaha block.
How do you do it?
Second is matching up a 3 cylinder OMC powerhead with a 40/50/60/70 1:64 gear case.
What is the best way to do it?
Cut and weld mids- use an adaptor plate above the gear case- use a custom powerhead base plate on the Mercury mid?
Any pictures?
Thanks

[Hounddog]

No replies yet so I am guessing there is no 49 cubic inch conversion from the 42 cubic inch 40/50 hp Yamaha. Too bad because it would certainly be superior to the 52 cubic inch Yamaha and there are lots of 40/50 outboards available.

[Ron Hill]

No replies yet so I am guessing there is no 49 cubic inch conversion from the 42 cubic inch 40/50 hp Yamaha. Too bad because it would certainly be superior to the 52 cubic inch Yamaha and there are lots of 40/50 outboards available.

Those Tiller guys know what is going on with drag rules (Mitch Hardee, Kent Foreman, Bill Kopod).

[88workcar]

Why limit yourself to 49ci? And no sir it will not be superior. I have a few 52ci spinning 8400rpm and making gobbs of power, a hot 42 don't stand a chance to that.

[Hounddog]

Why limit yourself to 49ci? And no sir it will not be superior. I have a few 52ci spinning 8400rpm and making gobbs of power, a hot 42 don't stand a chance to that.

I already have several 15 inch 70CES motors. The 49 modification provided it still used the 50 hp crank should have an advantage. The lighter weight of the motor and the smaller gearcase would also help. Have you ever seen a 49 ci mod 50 yamaha? I have not and I question if there is one.

[88workcar]

I have only heard of a 49ci 40/50 Yamaha. I also heard that you can go bigger but 49 was safest. Build it and see. A CES shares the lower with a 40/50. So you still have 52ci on top of the same lower. The lighter part may be worth some but so are 3 more cubes. You have to build it to see lol.

[Powerabout]

need to make a 3 cyl out of the sst45, then you have 100hp with stock porting at 7000

[hydrospeed77]

A CES shares the lower with a 40/50.

Not true. The original 3cyl 2-stroke 40/50 (700cc) lower is shorter in length and height, and has a smaller (diam) driveshaft. The casing will also not bolt up to a 70 (850cc) mid. The 70CES uses the same lower (aside from gear ratios compared to some) as the 48/55/60 2Cyl and some versions of the 50G (and some other 850cc) engines. The newer 4-stroke style 50 lower casing does bolt up to the 70CES (and standard 850cc 70) but the driveshaft splines are incorrect from the factory.

[Hounddog]

The 49 Yamaha would be interesting to build. The CES does not share the 40/50 gearcase, it has the 55 case. Making a 3 cylinder SST45 could be possible. I have seen mod 4 cylinder motors in snowmobiles made from two 2 cylinder motors. Years ago some mod outboard racers mounted 2 powerheads on a single tower.

[Powerabout]

It would mean making new 3 cyl crank and see if you could swing that in 56 case?
Thats the engine omc should have made as yam just marched in with bigger tripples and took tons of market

[Hounddog]

Based on the 56 OMC engine builds here in Canada a good drag motor would be oval port sleeves in a 1986 production cast block, mod 50 flywheel, Kevi baseplate and tuner, SST 60 gearcase with hooper billet carrier and 2 cylinder gears, a 12 1/2 X 24 thru hub Hill prop on a 13 foot Allison. Tuff to beat in 600 feet.

[filthy phill]

so you would put oval port sleeves in a bridgeport block .

what will you do about the the alloy bridge cast into the block itself. this would be visible with no sleeves in the block .(according to other on this site)...
would you cut this wall of alloy out the block or leave it in.

and why the cast block instead of the lost foam block, they are identical inside apart from a few glue lines, apart from the later cooling modifications made to the oval port block.

what would be the benefit in changing blocks ?
and the 2 cylinder gears being what ratio ? 2.42 or 1.86

[Ron Hill]

It would mean making new 3 cyl crank and see if you could swing that in 56 case?
Thats the engine OMC should have made as yam just marched in with bigger triples and took tons of market

I quote you, Powerabout, and I'm not sure you said it. But if OMC would have continued to make two stokes and sold them worldwide, (Meaning outside the USA) they'd never have gone broke. I think you said that to me on the phone one day.

Seems, as I recall, my brother, asked Charlie Strang, why the 49 cubic incher was the way it was? And the answer wasn't what my expected. The answer was the NEW $100,000 mill wasn't large enough......It something that!!! My brother said, "Really?"

Too bad, you didn't "Take Over" OMC, Powerabout. You could have made OMC Great........I'm not sure I'll use the word "AGAIN".

I'd argue with you abut Yamaha. They took the WHOLE MARKET.

[Hounddog]

so you would put oval port sleeves in a bridgeport block .

what will you do about the the alloy bridge cast into the block itself. this would be visible with no sleeves in the block .(according to other on this site)...
would you cut this wall of alloy out the block or leave it in.

and why the cast block instead of the lost foam block, they are identical inside apart from a few glue lines, apart from the later cooling modifications made to the oval port block.

what would be the benefit in changing blocks ?
and the 2 cylinder gears being what ratio ? 2.42 or 1.86
I would clean up the block and remove the bridge casting. The production block flows air better that the foam cast and even with the cooling mod to the foam cast, the production block is better. My thinking behind using the 2:42 gears is about hole shot, acceleration and 600 feet. The oval port motors running here have a big torque, low and mid range advantage over the bridge ports. A big diameter, big pitch prop turning slower will get out of the hole and accelerate faster with the 2:42 gears. You may need to repitch the 24 to 26 but if the motor is turn over 8000 for a second or two, it does not matter. Drag is about ET for 600 feet not speed reached at 600 feet. Only my opinion.

[filthy phill]

600 feet ? do you mean yards.

600 feet is just 200 yards
if its feet how long does it take for this race to be over ?

[Hounddog]

600 feet ? do you mean yards.

600 feet is just 200 yards
if its feet how long does it take for this race to be over ?

Their current rules posted on this site have the distance at 660 feet.

[Roflhat]

Does anyone know of any smaller lower units that will fit the 70ces? It's quite a lot bigger than the 50hp, I think you could fit a 14" diameter prop on the 70

Also maybe worth thinking about a modified tohatsu 50, you can bore them out and fit 40D 2 cylinder pistons (I think)

[filthy phill]

to fit small box on yamahaha do the same as most of the big boys, cut n shut.

But why would you want a small gear case ?

[Hounddog]

One of the problems with going to a smaller gearcase is the size of the prop shaft. The smaller cases have smaller and weaker prop shafts. You run big diameter and pitch on those smaller shafts and they will break. Since it is only 660 feet you may find a larger case works better. You would likely run the prop shaft even with the bottom of the boat. The larger case will lift the stern. So what if it runs out of water, it can have a drink at the end of the run.

[filthy phill]

Your dead right about large gearcase lifting the stern.
My boat is a bit front heavy and not a light boat for its size, but I know the faster I go the more the stern lifts, even with a prop not known to be good stern lifter.
the large area of the gearbox just wants to ride up on top of the water.

There are a few videos on youtube showing larger gearcases being very good for surface running at almost 100mph.
One video shows a large Honda with a big fat blunt gearcase riding happily on top of the water and staying on top nicely.

[sabine river killer]

small case / big case, interesting...

[Powerabout]

small case / big case, interesting...
how about the powerhead in your avatar on a 2.42, 9k+ at 600'??

[filthy phill]

From what I am understanding , these races are for a short length of just 660 FEET ? = 220- yards or 1/8th mile. ( 201.168 meters for the Europeans)

How many seconds do the boats take to complete these 660 feet runs on say a v hull of around 13 to 14 feet long ?

this I am very curious to know to compare what my little tub can do this distance in, .

[88workcar]

We just had our 1st race, last weekend. The winning rig at 894lbs with a 90 Yamaha ran a 9.46 on a stopwatch checked by many. We had 4 boats in our class, 56 total. It was a good time and I am hearing of 4 more to the next race, we got some folks fired up lol.

[Ron Hill]

Are there any results posted? When is the next race?

[filthy phill]

88 workcar
you wrote ...The winning rig at 894lbs with a 90 Yamaha ran a 9.46 on a stopwatch checked by many.

is that weight with or without the driver ?

[88workcar]

COMPLETE rig strait out of the water, had to weigh 880lbs Driver, helmet, jacket ect.. AS RACED

[filthy phill]

Well I am very suprised .
Thought the time would be lower with just that for total weight.
Must have pretty poor hole shot, but good on top end for straight line racing on
Longer distances.
Maybe this is why hound says about bigger gearbox being better for the drag.
.

[88workcar]

9.40s at 890+ lbs in 660' With a 3 cyl engine, idle in gear take off, no power adder, pump gas. Come on dude you didn't put much thought into that comment.

[filthy phill]

Well a 9.46 second boat would not embarrassing my little slow boat at all. I have crap 45 top end but gets to it quick. I know 100% she can do 660 feet well under 10 seconds.

[LittleCharger]

Well a 9.46 second boat would not embarrassing my little slow boat at all. I have crap 45 top end but gets to it quick. I know 100% she can do 660 feet well under 10 seconds.

You best check your math...they would put you on the trailer pretty quick

[Tim Kurcz]

61806Here's an answer to your gearcase lift issues: Water pickup low in the skeg leading edge. Get the entire case out of the water.

[Ron Hill]

I've been thinking this way for years. But I wanted to cast the gearcase in stainless so we could make the skeg thin as hell and strong.

WOW! Very cool!

[Powerabout]

61806Here's an answer to your gearcase lift issues: Water pickup low in the skeg leading edge. Get the entire case out of the water.

how to keep the bearing carrier in that?
Full solid and exhaust somewhere else?

[Tim Kurcz]

how to keep the bearing carrier in that?
Full solid and exhaust somewhere else?

The bearing carrier is epoxied in place per Hydroplay's recommendation. Exhaust path is through the (now above water) housing as required by APBA rules. So far, we've had no issues with the carrier coming loose. The same can't be said for clutch dogs and pinions which have proven to be the weak point (for the SST-60 housing). Then again, my powerheads over-deliver, and the driver is very aggressive.

A slotted 6061-T6 leading edge cuff and nose cone is welded to the gearcase and skeg. Though not skeg thin (a channel is needed for water), it adds strength at a small fraction of bullet frontal area. The cases (two built so far: one SST-60, one Hydroshift) handle better than the plow, and accelerate like crazy. We've not tested top end yet - props are all different. BTW: Ron supplied one of the props!

BTW: I'd provide more images, but the site is having upload challenges:-(

[88workcar]

I humbly invite you to our races sir, the more the merrier.

[88workcar]

Tim! you hacking my post? lol. I miss reading and seeing some of your stuff.

[Tim Kurcz]

Tim! you hacking my post? lol. I miss reading and seeing some of your stuff.

If only I lived closer, you'd see me on the course.

Just trying to be helpful and provide solutions to make your racing faster.

The new shop is just now ready for work. First up: Six 7-1/2" towers for the 45SS/OMC nitro gearcase. These use Mercury clamps are drilled for the OMC 45 twin and 49/56 triples, but can accept pretty much any power head.

The race never stops!

[Roflhat]

That's a really smart looking solution, nice work!

[Hounddog]

The first interest I have is building a 49 cubic inch out of the 3 cylinder 40/50 hp Yamaha block.
How do you do it?
Second is matching up a 3 cylinder OMC powerhead with a 40/50/60/70 1:64 gear case.
What is the best way to do it?
Cut and weld mids- use an adaptor plate above the gear case- use a custom powerhead base plate on the Mercury mid?
Any pictures?
Thanks

NOW THE MOTOR ON THIS BOAT IS INTERESTING!!
Look at the horsepower listed. 75 HP

http://www.screamandfly.com/showthread.php?326463-Mirage-Tomcat-with-Yamaha-50hp

The mid is a 50 hp short shaft. Did Hydro Tec rework a 52 cubic inch to fit or did they built it out of a 42 cubic inch or is it Fake News in the ad??

[Roflhat]

Wouldn't have thought a bigger powerhead would fit under a 50hp cowl, I suspect it's just a tuned 50hp

[filthy phill]

the way I read it is they took the 50hp block done a bit of work and bumped up the hp to 75hp at the prop,
so I doubt very much its just a 75 hp block fitting under there.
if the 75 block was fitted then I am sure he would be claiming much higher horsepower from hydrotec ( 85 - 95 etc)..

[Hounddog]

No replies yet so I am guessing there is no 49 cubic inch conversion from the 42 cubic inch 40/50 hp Yamaha. Too bad because it would certainly be superior to the 52 cubic inch Yamaha and there are lots of 40/50 outboards available.

This thread is about the 42 mod to 49 conversion. It is said to produce horsepower in the 75 range. I posted the Hydro Tec motor since it was posted in the ad at 75 hp. I wondered if it was a big bore mod 50 Yamaha. It would be difficult to get 75 hp out of the 42 cubic inch . If it is 75 hp many of us would want that motor.

[88workcar]

Love reading the old stuff, I have since built a 42ci mild build. It made 69hp and spun to 8200. Stock bore stock stroke, If I spend a little time on r&d there is more there.

[Hounddog]

Love reading the old stuff, I have since built a 42ci mild build. It made 69hp and spun to 8200. Stock bore stock stroke, If I spend a little time on r&d there is more there.

It is impressive how the 3 cylinder 42 cubic inch Yamaha and especially the 50 hp Tohatsu have broken many of the speed records in the last few years.
In 2013 a 50 hp Tohatsu raised the speed record in T750 over 10 mph to the current record of 66.69 mph.
In 2015 a 50 hp Tohatsu set a new speed record in SLT Pro Stock at 62.99 mph.
Even more impressive in 2015 a MOD 50 Tohatsu set the MOD750 SLT record at 71.35 mph.
Over the years we have read about 70 hp carbs, custom cylinder heads and custom tuners being used on these motors.
But, none of those motors got close to 71 mph.
I for one would be very interested hearing from people in the know just how they do it.