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  1. #1

    Polaris jet pump cavitating (ventilating)

    Hi Guys,

    Im new to this forum, but hoping you can help me. I have a Polaris Virage 700 (2001). I took it our around 2 months ago and it felt like is was cavitating in the water. This only happens on take off. When the ski is off the blocks it goes like the clappers, no problems.

    So i stripped out the pump to check the impeller and wear ring (was a bit shabby, so replaced the whole lot) new wear ring and solas impeller etc... Fitted it all back together and its better, but still feels like its cavitating from standing start. It almost feels like a clutch slipping in comparison.

    Any ideas guys? Any help wolud be great.


    Regards

    Tom
    Last edited by K447; 03-08-2013 at 01:14 PM.


  2. #2
    Banned User
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    Check the ride plate and make sure its sealed to the hull. The impeller to wear ring clearance should be .010 or less to be optimal. It may never feel like it just grabs and goes, there isnt a ton of acceleration to be had from a 700. Check those things out and report back.

  3. #3
    ripcuda's Avatar
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    Welcome to Green Hulk!

    I'll second Bryan's thoughts... ride plate seal.

    When I overhauled my SLT750 jet pump... I started cavitating REAL bad. I couldn't even get on plane. Turned out to be sucking air from around the jet pump above the ride plate in the pump tunnel area through the front ride plate / intake grate joint. All my ride plate sealant was old and washed out. Re-sealed the ride plate and it hasn't cavitated since.

    Cheers!

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Sounds like ventilation of the jet pump, not cavitation

    Agree that it sounds like the sealing around ride plate and jet pump intake area is leaking air into the jet pump suction zone.

    Everything forward of the impeller is under suction when powering up from low speed or idle.

    Air leaks cause the impeller to ventilate as it tries to pump the incoming water through with air bubbles mixed in. The effect is that the impeller spins up but does not properly pump the water out the back so thrust is greatly reduced.

    As the hull speed increases eventually the water pressure becomes positive in front of the impeller and any sealing leaks change from air leaks IN to water leaks OUT. It feels like the jet pump finally 'hooks up' and acceleration improves markedly.

  5. #5
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    check the driveshaft seal assembly well.
    Last edited by K447; 03-05-2013 at 10:36 PM.

  6. #6
    I have orderd a new drive shaft seal pack also (waiting for delivery), as I had a feeling it might be drawing air in.

    Thanks very much for all your imput, Ill go grab some sealent and get started later.

    cheers

  7. #7
    Connecticut CrazyA's Avatar
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    Quote Originally Posted by TxPro1200 View Post
    check the driveshaft seal assembly well.
    I've had the same thing happen on a Virage. Not saying that's it, but check 11, 12, and 13. I've seen the nuts come loose or crack.
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  8. #8
    Just a quick update.

    pulled the ride plate off today, but before I did I noticed some pretty large gaps around the ride plate leading into tunnel, where its bonded onto the hull. I got a hot air gun out and heated up the old plate to help supple up the sealer and off she popped pretty quick. I would advise anyone to do this or you could spend forever and a day getting it off. Heat did the trick!

    touch wood it should have sorted out the problem.

    Water test tommorw, so fingers crossed guys! let you know how I get on.

    Cheers

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by motosyko View Post
    Just a quick update.

    pulled the ride plate off today, but before I did I noticed some pretty large gaps around the ride plate leading into tunnel, where its bonded onto the hull. I got a hot air gun out and heated up the old plate to help supple up the sealer and off she popped pretty quick. I would advise anyone to do this or you could spend forever and a day getting it off. Heat did the trick!

    touch wood it should have sorted out the problem.

    Water test tommorw, so fingers crossed guys! let you know how I get on.

    Cheers
    While you have the ride plate off, inspect that threaded plastic through hull fitting that CrazyA pointed out.

    With the ride plate off, did you identify places where the sealant was definitely not sealing properly?

  10. #10
    well, Well!

    Took her out for a water test today, and it hooked up like lightning! Went off like a bullet! That certainly sorted out the problems, but im amazed how such a little thing can cause such a big issue.

    I just want to say to all the guys that helpted me out with advice, a big thanks! You guys on this forum know your S*%t, keep up with the good work!

    Once again big thanks


    Im off for a play!

    Cheers

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