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  1. #1

    ‘96 Seadoo GSX (787) Intermitting Speed/RPM Issues

    I have a ’96 Seadoo GSX that runs great except; it won’t always reach top speed/rpm. To reach top speed/RPM is sometimes tough.

    Here’s what I have to do to reach maximum speed/RPM.
    1. Simply pin-it and it reaches 6,000+ RPMs (this works less than ~ 20% of the time)
    2. Yo-yo the throttle a few times and it reaches 6,000+ RPMs (this works about 20-30% of the time)
    3. (or) Jump a wake or bounce hard while pinning the throttle (this works EVERY time 100%)
    * Otherwise it hovers around 4,800 RPM and acts like it wants to go faster.

    Here’s the stuff you need to know.
    I bought the craft with a blown engine. I’m a retired aircraft mechanic. I rebuilt it but let it sit in the garage a few years before I gained more interest.
    · Motor is a fresh rebuild (less than 8-10 hours) punched1st over. New crank, bores, pistons, rings & bearings. Crankcase pressure tested.
    · New Fuel lines replaced & Fuel Petcock cleaned @ 0 hours + carb refurbish
    · Fresh gas (drained the tank and refilled)
    · New plugs (changed several times)
    · Compression (MAG 155 psi, PTO 154 psi)
    · Completely rebuilt both carbs (soaked for several hours in Berryman Chem-Dip and blow out with air and cleared with wire. All brand new gaskets & rubber (except needles and main – they look perfect) pop-off set.
    · Cleaned RAVE Valves (look brand new)
    · Replaced RAVE Bellows (green), gaskets and o-rings. Added zip-locs to bottom of bellows
    · New pump wear ring replaced (less than 4 hours)

    I’m starting to think that it’s the regulator on the waterboxor a waterbox baffle issue. I’m better at Polaris PWC issues than Seadoo.

    Help a brother out.

    Last edited by skooter; 08-27-2013 at 01:50 PM.

  2. #2

  3. #3
    canuck's Avatar
    Join Date
    May 2006
    The wet left coast.
    Does it have the correct impeller ?

    I had an old GSI that was bought not running and it had similar symptoms. With two people it could not get on plane, with one person it would take a little coaxing to get on plane and when it did it felt fast. In cool weather the problem was not as pronounced as in warm weather. After about a year of checking and trying multiple things it turned out the previous owner had put a steeper pitched impeller in it that came off a 787 powered ski and the poor little 717 did not have the grunt to spin it. I got the correct pitch impeller and it felt like a totally different machine.

  4. #4
    Thanks. canuck.

    I'll try installing another prop. I have a few lying around from tear downs.


  5. #5
    On my 1996 GTX this past weekend it would surge between 4800-6500 rpm. I put some 93 octane fuel in it. Runs like a top now.

  6. #6
    ou812's Avatar
    Join Date
    Jun 2006
    My 97 gsx did the same thing. It would run normal for about 3 minutes then drop 1000 rpm. I swapped out everthing I could think of... finally one day it just died... no blown motor or anything. .. just stopped running and wouldn't even turn over. It turned out to be a broken pickup inside the mag cover. It was cracked for a while I could tell and it was throwing my timing out all over the place. It's been fine ever since then after it was replaced. There is an updated mount on those sensors with 2 tabs instead of one... its worth a look.

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