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I have å 1989 model 9,9 ho and would like to increase the power to 15 hp, what parts do I need to change? Newer models have å stopper on the carb, but I think this model needs new reeds and main jet? Is the carb bore the same for both models? Appreciate your help, so I can order parts asap.
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Not sure, I don't attempt to modify horsepower on an engine. -
Hi, I wanted to do the same thing to my 9.9 . I called a local Yamaha Mechanic and asked him if this was possible and he informed me that it was against the law and he recommended that I not do anything to the 1997 Yamaha 9.9. He stated that since the EPA has gotten real involved in setting up and certifying the HP ratings in these engines he was forbidden to even talk about how it could be done. However, having said all that, if a person wanted to proceed and do this himself, all that would have to be done is a little research on your particular engine and compare the part differences between yours and a 15 and it might be possible to just replace the 9.9 reed valve assembly with a 15 hp reed valve assembly and possibly replace any other parts that are different and then do the proper adjustments per the 15 HP Specifications and you might, just maybe end up with a 15 HP but there is no guarantee, and I would proceed very cautiously, because you would be assuming full liability if something happened and the engine blew up and hurt someone.Comment
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So does that make you want to go try it yourself?Comment
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