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Thread: Newbie Question

  1. #1

    Newbie Question

    Hello All,
    Very new to this site (been reading for hours now) and fairly new to modding jetskis. I have 2 1990 Yamaha's Waverunner III 650 that I keep at my lake cabin for the kids to play with. I decided last year at the end of the season to pull the engine on one of them to rebuild. I had already rebuilt the other one 3 years ago and did 0.50 oversize pistons (blew a head gasket on that one just before the rebuild).

    The ski I am about to rebuild was rebuilt by a shop about 4 years ago. The one I rebuilt 3 years ago myself does circles around the other one which is why I decided to rebuild it myself this year.

    So before I go and do the rebuild with the second ski, is there something else I can do besides piston oversize to increase power slightly? I am not familiar with these enough to know what can be done to these humble engines. Again it's only my kids who use them which is why I like them because they do not do killer speed but I would like to give them a little more boost.

    Thanks in advance for any advise...

  2. #2

    Join Date
    Aug 2006
    These engines respond VERY well to mild porting and more compression. I have done several and though its hard to believe, a Wave 3 can get to 50 mph ( stock around 36 mph). has all the info about mods to these engines, and they are turn key and reliable, plus it doesn't hurt fuel economy.

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