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  1. #1

    1999 GP760 is dying during throttle only in the water

    I had the 99 GP760 out last weekend for a few hours and it ran great. This weekend, I dropped it in the water and it fired up and idoled but as soon as you accelerate it would die. It would fire back up, but die every time you accelerate. I took it out of the water it it fires up and can rev no problem. I did take the head off and replace the head gasket between last weekend and this weekend, but that is the only thing I did. All bolts are tightened to spec. I checked spark plugs and the little thing that screws on top of the spark plug came off inside the spark plug wire. Plugs were a bit black (rich), so I went ahead and replaced the plugs (BR8ES). Carbs were just rebuilt by OSB a couple months ago, so gas and spark should be good. Any thoughts? I will try to do compression test tonight.

    1) Possible Air leak?
    2) If battery is strong enough to start the ski, is should not affect keeping it running right?
    3) Fuel pump? Not getting enough gas to accelerate?

    Thanks GH

    Compression is 165psi in both cylinders.
    Any sugguestions on where to look next are greatly appreciated.

  2. #2
    i will get all the rest i need when im dead corkycat's Avatar
    Join Date
    Jan 2009
    could be air leak from the carbs, or maybe the carbs need refurb? when were they last refurbed and how many hrs has your ski got, if batt is strong enough to start then thats all the batt does, if batt was knackered it would not affect the running as once the ski is running you can remove the batt altogether and the ski remains running..
    defo carbs in my opinion

  3. #3
    carbs were rebuild by OSideBill so I know they are good, but they were installed by myself so they is where I will start. Thanks and if anyone has any additional thoughts I would definately appreciate them. It ran just fine the weekend before.

    Any thought about plug wires?

  4. #4
    nscrnt88's Avatar
    Join Date
    Jun 2010
    central florida
    new to the pwc world but not marine engines. had the exact same problem with my 90 hp merc. ran like a top on the hose, but put it in the water and it puked all over itself. my problem was the carbs. as you just had yours rebuilt thats not the obvious answer so the problem is likely either before or after the carbs...... is enough fuel getting to them... or is there air leaks to the motor.

    running it out of the water "on the hose" does not put a load on the engine, there for it does not require the same amount of fuel as it would when its in the water. been there done that just my experience, hope it helps.

  5. #5
    Ok - I ordered a new fuel filter and hopefully my old is just clogged. Do these skis have known issues with the fuel sending unit??

  6. #6
    Budman's Avatar
    Join Date
    Jul 2008
    I haven't heard of bad fuel sending units but I have read about bad fuel selectors. Try turning it to reserve and see if that makes any difference.

  7. #7
    I tried both "ON" and "RESERVE" with the same results. Is there a filter in the sending unit that may be clogged?

  8. #8
    Moderator OsideBill's Avatar
    Join Date
    Mar 2006
    United States
    The back fire says lean to me, Air leak or check the fuel supply. like everyone has said fuel selector, filter and yes the sending unit pick-up. it has the same known issues with the screen and flapper door. Back fires can damage reeds, so yes do a compression test. if it is low, check to make sure you did not damage a reed

  9. #9
    I did a compression thest and it was 165psi on both with ProTech head. The ski has never backfired. It just dies when given throttle when in the water. It will not die when given throttle on the hose. I will start to look at fuel delivery and possible air leak. The frustration part is that since putting the carbs back on, we have been out 3-4 times at a few hours each time with no problems...

  10. #10
    Moderator OsideBill's Avatar
    Join Date
    Mar 2006
    United States
    There is a screen in the sending unit check that. oh yeah remember that sheet I sent with the carbs? new fuel filter is highly recommended with your fresh rebuilt carbs Just messing with you Keith. call me if you want.

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