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Thread: 70 hp Yamaha Questions

  1. #1
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    Default 70 hp Yamaha Questions

    Ive got a 70 Hp Yamaha 2 Stroke, I know what im going to do motor wise, but what can be done lower unit wise? I really think the 2.33 ratio is going to end up hurting my performance. Are there different gears available? Or should I just go to a smaller lower unit and make a custom mount to bolt everything up?

  2. #2
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    Well considering the UIM record for that motor is 102.5mph there probably lots to be done...
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    1.87 gear lowerunit from a 48 or 55hp bolts right on.

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    Thank you sir!

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    i,ve been told the uim 70ces t850 ran 1.73 gear ratio.or they run 1.86 ratio stock 48/55 ratio.correct me if im wrong.

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    Found this old thread that mentions the 102 mph record. I hope the picture is not the record setting boat. That does not look like it could run that speed. Not even a nose cone. Were you allowed to run an oversized skeg?

  7. #7
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    looks like it has a low water pickup on the hull

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

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    Canada vs france?

  9. #9
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    No, its not the record holder. This pic was shot during the Rouen endurance race a few years back - before the yammie 70 was outlawed.
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