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  1. #1
    07STX15's Avatar
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    Jet pump hesitation before acceleration???

    Ok, Im turning to the GH experts here for help. Long story short, I mod'ed my STX15f (2007) and just got the pump back form Skiworx gettign rebuilt. Put it on, took it out, and when I first hit the throttle, the RPMS shoot up to 8k and barely any forward movement. After 3-5 seconds, it seems the pump/impeller/dunno catches up and takes off. Anyone else had this issue? ANyone know what it may be?

    Some more background info to cover the questions: RPM kit installed as instructed, free flow exhaust mod with re-routed waterline, replaced solas concord 14/21 with new (same model same pitch as before), R&D ride plate, spindles on drive shaft look good (no wear)


    Im thinking cavitation. Could it be?


  2. #2
    steve45's Avatar
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    I'm not familiar with the pump on that model. Did you put any sealant anywhere when you put it back together? I don't know if you're supposed to or not.

  3. #3
    nicjak's Avatar
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    yep cavitation either wrong pitch, badly worn or installed incorrectly

  4. #4
    07STX15's Avatar
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    Quote Originally Posted by steve45 View Post
    I'm not familiar with the pump on that model. Did you put any sealant anywhere when you put it back together? I don't know if you're supposed to or not.
    Steve, yes I did. When installing the Adjust-a-thrust shuttle cone, it says to put a bead of silicone on the face where the shuttlecone face and pump face meet (to ensure water tight seal). Thats the only place.

  5. #5
    07STX15's Avatar
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    Quote Originally Posted by nicjak View Post
    yep cavitation either wrong pitch, badly worn or installed incorrectly
    nicjak, thats what Im thinking. I dont think its the wrong pitch because I replaced the impeller I used all year last year (with no problems). it had a Solas COncord 14/21 on it, and I replace dit with the same thing, same pitch. When installing, Im pretty sure I done it right. Installed it on a shorter impeller shaft that came along with the shuttle cone assy (after market).

    Should I be looking for an anti-cavitation cone for this? i seen one for the Ultra LX, not for the 15 though. Should I replace my pump? Im thinking a Skat trak magnum, but I heard unless you have seriously upgraded your HP from stock (like adding a SC or Turbo), it isnt
    worth the money. Any guidance would help. Thanks for the gudance I got already. Thanks.

  6. #6
    07STX15's Avatar
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    UPDATE: After tweeking with the pump and impeller, it seems my problems have gotten worse. Now, even with feathering the throttle, it seems when I hit the gas the motor spins, but no forward motion other than a slow idle (with RPMs maxed out). very low RPMs (idle speed) can get some thrust and torque, but as soon as you give it a significant amount of throttle, its just bogs. Any ideas guys?

  7. #7
    07STX15's Avatar
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    Quote Originally Posted by 07STX15 View Post
    UPDATE: After tweeking with the pump and impeller, it seems my problems have gotten worse. Now, even with feathering the throttle, it seems when I hit the gas the motor spins, but no forward motion other than a slow idle (with RPMs maxed out). very low RPMs (idle speed) can get some thrust and torque, but as soon as you give it a significant amount of throttle, its just bogs. Any ideas guys?
    UPDATE UPDATE: ok im a f*n retard for not noticing this before, but would not having the rubber gasket/ seal on the impeller side of the jet pump be causing this cavitation? DOH! Yes I think so. Im going to order that seal and report back my findings. Please no hurtful comments guys. Pray to the ski gods this is my fix!

  8. #8
    nicjak's Avatar
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    hey we didnt call you a retard you did

  9. #9
    steve45's Avatar
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    Well, you won't make that mistake again!

  10. #10
    07STX15's Avatar
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    Quote Originally Posted by steve45 View Post
    Well, you won't make that mistake again!
    no indeed not! well at least ive learned my lesson; always ALWAYS look over your equipment before installing.

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