550/750 conversion cavitation
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  1. #1
    PWCToday Regular jlunde's Avatar
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    550/750 conversion cavitation

    running rhaas pump swap with 10/16 140mm Hooker and solas scoop intake. the ski is great at high speed and throttle response i good. but it does spin out while cornering and seems to cavitate.
    almost feels like doing a burn out in your car.....ive heard of guys running a deep 2 bar style intake, would that help? anyone have any good results with staying hooked up?

  2. #2
    PWCToday.com Is My Home Away From Home BLRider's Avatar
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    Re: 550/750 conversion cavitation

    Somewhere you have a gap in your pump gasket that is giving you this symptom.
    Never argue with an idiot, they will drag you down to their level then beat you with experience.

  3. #3
    PWCToday Regular jlunde's Avatar
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    Re: 550/750 conversion cavitation

    Quote Originally Posted by BLRider View Post
    Somewhere you have a gap in your pump gasket that is giving you this symptom.


    Yah I thought that might be possible...just wana make sure it isn't something that can be changed or swapped out...I think we both know what a pain it is to pull that pump out

  4. #4
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: 550/750 conversion cavitation

    Need to know a bit more about your set up too. I was running a 10/16 with a 750 dual carb engine. Limited, no porting. 80mm nozzle, PJS pipe, Supertrap waterbox, stock ignition. 10/16 was perfect with that and the ski ran a best of 55.8 mph.

    Besides the cavitation, is there much vibration? That's a good indicator of how well everything is aligned too. Getting this conversion right takes a lot of time. I talked to a local stand up jet ski shop a while ago, and the 2-3 builds they personally had been involved with they could never get all the vibration out of the driveline.

    I also found that when my ski had perfect alignment, the gasket would not fit. The pump was too close to the hull at the top. I also found that there was a gap between the pump shoe and pump mounting surfaces. I filled this section with epoxy putty, lubricated the pump mounting surface, and later when I broke it free the gap was filled. I sanded it flat a bit and it was perfect. Then from that point on, instead of using the gasket, I would install the pump and then press in and wipe smooth more epoxy putty from the impeller side, down the inlet tract. When I had to change impellers, I could break the pump free, just disrupting this small gap. It was way faster for me to make sure this surface was perfect and re-apply the epoxy putty than to try and get the gasket to work. More details are in my build thread in the individual builds section.

    I have speculated before that it's possible the hull angle which the shoe mounts too has some significant tolerance variation. Either ski to ski or year to year. Since this surface is not used for anything at all on the JS/ SX pump mounting, Kawasaki could have the tolerance on those dimensions/ angles as wide open as they felt reasonable. On some hulls the shoe mounts up perfect. On others it requires a lot of work. On my next hull, before I mount the shoe up, I am going to assemble everything together and see if I can get an idea if a shim is necessary, between the hull and shoe.

    Hope that helps. A little work is worth it. In the end my ski had less vibration than I think both my 09 SJs had stock.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
    3DR hull mods [TBD]



  5. #5
    PWCToday Guru dose's Avatar
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    Re: 550/750 conversion cavitation

    I couldnt get the pump in with that blue gasket either, i just used a little silicone, no cavitation
    super couch
    550sx with 701 and big pump
    550 RC-520
    809cc X2

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