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  1. #1

    SLT 750 has vibration and then power loss after 1/4 throttle

    So if I have the jet ski on the trailer in the water, I can run it at full throttle and get no vibration (sometimes if I blip the throttle, I get some slow response -- probably need to clean the carbs) and the pump is really making the water flow like it wants to run.

    So then I take it on the lake and run it and once I get over 1/4 throttle, the jet ski starts bucking and vibrating and it sounds like knocking and clanging. I then put it back on the trailer and run it in the water and it runs fine again. Take it back out on the lake and runs like crap.

    All pistons are firing as I can unhook each spark plug wire and it make a noticeable difference in sound. I can put my hand on each cylinder and hold it there for 3 seconds without too much pain....not really over heating. I don't have a hole in top of any cylinder. I can put a pencil into the cylinder and using the eraser end pushing down or side to side....I can't make the piston move around (no cylinder slap).

    The engine mounts are solid and I can't move the engine any.

    The impeller has some damage. The silver part of the impeller (the rotating blades look like they have started scraping the outside as I can see some circular grinding. The leading edge of the black fins have damage too. 3 of the 5 black fins have a nickel size chunk taken out and the 4th one has a dime size chunk.

    So what is the verdict on the craziness?


  2. #2
    The leading edge of the silver part of the impeller that first grabs the water and pushes it thru the system doesn't have any chunks taken out and looks good. I can see where it looks like the outer edge has been grinding on the outside though from the circular grinding pattern.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by DougyD19 View Post
    The leading edge of the silver part of the impeller that first grabs the water and pushes it thru the system doesn't have any chunks taken out and looks good. I can see where it looks like the outer edge has been grinding on the outside though from the circular grinding pattern.
    Have you actually removed the jet pump and inspected it?

    In particular checking the impeller stub shaft bearings for radial slop or gritty feeling when turning.

  4. #4
    I will pull the pump tonight. Will that make a popping sound/start vibrating the whole jet ski and make it slow down after about 1/4 throttle and above? Why would I have the sympton running on the lake and not on the trailer in the water?

  5. #5
    BlueFishCrisis's Avatar
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    Quote Originally Posted by DougyD19 View Post
    I will pull the pump tonight. Will that make a popping sound/start vibrating the whole jet ski and make it slow down after about 1/4 throttle and above? Why would I have the sympton running on the lake and not on the trailer in the water?
    It could have something to do with it, and is a good maintenance check anyway. Check also that your intake grate is secure as well as the ride plate. These are the only two pieces that will be affected by hull movement in the water. If the grate is loose or a bolt is missing, it will create a lot of drag, unwanted vibration, reduced speed, and disrupt the water flow into the pump.

  6. #6
    The problem was a broken reverse cable that would pop up and down and that was the popping sound. It did sound like it came from the engine, but it was not the engine. Put a new cable in and all is good.

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