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  1. #1

    Join Date
    Sep 2016

    STX-15F down on speed/ power. What am I missing?

    Howdy everyone! Hope to utilize the knowledge of everyone on this great resource and get my ski running great.

    I have a super low hour (under 50) 2004 STX-15F. It has only been on freshwater here in AZ

    As it sits, I can only occasionally get the thing spinning up to 7000 RPM, topping out at 53-54 MPH on GPS. ( it has never gone faster since I have owned it, about 7 years.. it has sat a lot)

    Here is what I have done & tested so far this year...

    Brand new fuel pump/ fuel regulator ( OEM)
    New fuel filter (aftermarket )
    Gas tank drained/cleaned
    Installed a fuel pressure gauge on the rail, seems to be between 40-50 PSI at idle

    Injectors professionally cleaned & tested at shop in Tempe

    Compression test (each cylinder ~200 psi on my crappy HF gauge). Wasn't so much worried about the psi , since there was little variance between them
    New ride plate (polished shiny. epoxy over mounting holes)
    went back to OEM intake grate (had a worx one on, ski only ran around 50 previously )
    New spark plugs ( 2 electrode CR9EK plugs)

    Throttle body hits open position limit tab when holding at WOT

    Looked for exhaust leaks, also tried running with the seat off (ran a little happier, but nothing crazy)

    The jet pump has a defect free solas 14/20 impeller
    clearances to the housing are tight, no noticeable cavitation

    Jet pump bearings are still original. I don't have anything to judge based on the feel. They feel smooth quiet and somewhat tight when spinning just the shaft. Spins with the impeller on easily.

    The ski should spin a 14/20 prop no problem right? It does have aftermarket sponsons , these shouldn't be slowing me down that much though?

    Anyone have anything else they can think of worth trying?


  2. #2
    That's pretty much normal, maybe a tiny bit low. Indicated speed is just an estimate with many PWCs. Mine indicates 100-103 KPH as does my brother's RXP running next to me for comparison however GPS is in the low 90s (55 mph). It's been like that since new and has 600 hours on it so I'd say do not worry about it, that is what I would try if I were you. Mine will vary a bit depending on air density and can be seen as a slight change in maximum rpm, but the lowest I ever see at seal level is 7 grand.

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