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  1. #1

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    Measuring Impeller Clearance

    So, I'm trying to figure out if the impellers on my jet boat (Yamaha Exciter 220) are worn beyond reasonable limit. The manual states the max clearance to be 0.024". If i run a pin gage around the outside of the impeller, I get about 0.023" clearance on the trailing edge of the blades, but much more on the leading edge, at least 0.035". My question is: should this be like this, or should the clearance be constant from the leading to trailing edge of the blade? i'm experiencing pretty bad cavitation from stopped, and trying to hunt down the cause.

    Thanks!
    -Matt


  2. #2

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    Impressive! Not a single response!

  3. #3
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    Thats your cause of cavitation, you should have no more than 0.024" anywhere.

  4. #4
    USCME's Avatar
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    If it helps at all, here's a pic of my stock prop on a gp1200r. Just from looking at it, the clearance between the prop and wear ring appear to be constant all the way around. Sounds like a new prop or wear ring would solve your problem.

  5. #5

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    Wow, that's a lot better! The pic of your stock prop actually tells me a LOT; it looks way different than mine. I have very obvious gaps b/w the edge of my impeller and its housing. It looks as if the prop was intentionally shaped with the leading edge having significantly more clearance than the trailing. Thanks so much for that fantastic response!

  6. #6
    USCME's Avatar
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    No problem, hope you get your problem worked out. Let us know if there's anything else we can help with

  7. #7
    Moderator OsideBill's Avatar
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    cavitation can also be caused by air leaks in the pump shoe and transom plate. not sure what the boat set-up looks like but on the skis there is a foam seal where the pump shoe meets the transom plate and if this is blown out they cavitate bad.

  8. #8
    I'm still new to the world of PWC's.. can someone show me a picture of where the pump shoe is?

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