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

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

    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
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    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.

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    Quote Originally Posted by Hounddog View Post
    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).

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    Team Member 88workcar's Avatar
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    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.
    Helping folks out around the globe.

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    Quote Originally Posted by 88workcar View Post
    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.
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    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.
    Helping folks out around the globe.

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    Quote Originally Posted by Hounddog View Post
    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.

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    Team Member 88workcar's Avatar
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    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.
    Helping folks out around the globe.

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    Quote Originally Posted by 88workcar View Post
    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.

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    Quote Originally Posted by Hounddog View Post
    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/showthre...th-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??

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