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  1. #1

    GP1200 engine runs strong but low speed why?

    I just got my GP1200 tuned pretty good. Its WOT RPM is between 6940-6960 on flat water. This is only after I shimmed the R&D rideplate so it would stop porpoising. Unfortunately its only doing about 50MPH on the factory speedo. I know these aren;t accurate but it also feels like its not getting top speed like it should.

    I will check the actual top speed with GPS in a couple days but in the meantime what can I check that could be slowing me down? The engine runs real strong and pulls pretty hard not much cavitation. The ski porpoised like crazy before I shimmed the plate and its still a little squirly in chop but OK on flat water.

    The ski has:
    R&D rideplate
    R&D intake grate
    K&N flame arrestors

    Everything else appears stock I'm not sure what impeller is on it (I'm assuming stock but maybe not). Any ideas? Oh and it sounds like a beast much deeper than my GPR but the exahust looks stock.

  2. #2
    Geez no one knows?

  3. #3
    Join Date
    Apr 2006
    Orange, TX
    Get a topspeed with a GPS. My speedo always read low before I removed it. Get a true speed and we will go from there.

  4. #4
    Will do this weekend just figured there was something I can check in the meantime.

  5. #5
    Nothin' runs like a Deere IowanGPR's Avatar
    Join Date
    Sep 2006
    Waterloo, IA
    make sure you didn't shim it down too far and its not hanging an catching water. did you seal your pump shoe? or modify that in any way?

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