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  1. #1

    Exclamation Seadoo XP bogging down/misfiring

    Just brought a 1999 XP LTD 951, rebuilt by previous owner but never run in and has been sitting for a couple of years.

    Ran fine for the first hour, then suddenly it started bogging down between 2500rpm and 4500rpm. It bogs down and tries to die, and starts surging etc (as if not getting enough fuel). Have pulled the carbs apart and cleaned everything and pulled jets out, but now it's even worse and bogs down at all revs, and will die unless the throttle is held wide open (even then it misfires and splutters, and revs won't go past 5000rpm).

    Have replaced the fuel hose, and cleaned the three filters (main filter and 2 x carb filter). Seems to be good fuel flow right to the carburetor. Has fresh 95 octane fuel in the tank (only 10L or so). Have low speed mixture set at factory setting of 1.75 turns, and high speed is wound right in (lean, as this was how it was from the start when it used to run ok). Any other settings I may have incorrect?

    So gutted as I purchased it for the holiday season but it's not going! Any help would be much appreciated.

  2. #2
    race jase's Avatar
    Join Date
    Feb 2007
    auckland nz
    Factory settings a low 1.1/4-1.5 turns from seated and high is seated to .5
    Has your ski got aftermarket filters by any chance?


  3. #3
    Nope standard engine etc. Thanks for those settings.

  4. #4
    20 feet Boy's Avatar
    Join Date
    Jul 2010
    Bend OR
    Most people don't change the fuel lines air bleeding valves line. That lets air in and out. Sometimes the lower one under the bumper on the side of the ski plugs up. Mine had oil in it and had plug it up.Take off the line to the tank and put a rag on it to see if any thing comes out. then you take a air compressor to out side of valve blowing in to valve. Make sure to take off inside line or you will blow crap into full tank maybe. I thought this might help. If not sorry for wasting your time. It sound like it might have more of a problem then this.

  5. #5
    sound like a your rectifier could be at fault and its putting AC volts in the battery insted of DC your coil pack runs off the battary and needs dc volts to run. it could be missfiring as its getting a AV wave the rectifier changes this from ac to dc. i had one go on me like that on a 787

  6. #6
    Yes this is something I have been wondering about for awhile, what are the common symptoms? And whats the best way to diagnose a broken rectifier?

    Cheers in advance and merry Xmas!

  7. #7
    get a voltsmeter and set it to 20v DC start the ski and check if its charging should be up like 1350.1450volts.. in the grey box at the front of the ski. is where u will find it..most have 3 yellow wires and one has a Red wire.. if u unplug the red wire and start the ski it will just be running off battery volts but will be about 12.50 volts when running thats the best test..

    if that doesnt do it check your compresson..

  8. #8
    The rectifier on a 99 is integral to the MPEM,it is not a separate device like on the 787 engines, so it cannot easily be disconnected like on the 787's for testing. You can use a multimeter and test it by first measuring the DC voltage while revving it up. Should be higher than at rest, but no higher than 15 VDC. Then switch the meter to AC and measure the AC ripple, should not be more than about 200 millivolts while revving it up.

    Ryan has posted this problem on multiple threads and has not yet checked the logical things like the rave pulse one-way valve and supply line, which will cause symptoms like he described.

  9. #9
    I've checked compression, and both cylinders are exactly the same at 105psi, I realize this is low but I'm sure it's due to the fact it's still being run in? Its only had about 1.5hr running time if that.

    I've put a voltmeter on the battery and revved to 5000rpm, doesn't go past 12.5V approx., so I'm guessing this means its ok as it isn't going past 15VDC?

    Sea Dood, sorry I've missed the RAVE pulse line, what's the best way to check the one way valve? I'm guessing you are reffering to the solenoid kinda thing underneath the hood which controls the RAVE's?

  10. #10
    Let me explain the RAVE system so you can check it over thoroughly. The raves on a 951 open with pressurized air. They are closed until about 5,000 RPM, then opened to allow the engine to rev higher.

    They get the pressurized air from the PTO crankcase. Under the PTO carb, there is a short line that goes from the nipple to a small plastic one-way valve. On the other side of this valve, there is a hose that goes up to the black solenoid you are referring to. From the solenoid, a line goes to both RAVEs. Pressurized pulsed in the PTO crankcase are passed through the one-way valve, so pressure builds up in the line going up to the solenoid. When the engine hits about 5K RPM, the MPEM opens up the solenoid, allowing pressure to open the RAVE valves.

    It is very typical for the short line from the crankcase nipple to the one-way valve to split. Also, the one-way valves tend to gum up and either not allow pressure to go thru it, or stick open so the plus/minus pulsing in the crankcase goes thru it. In any event, the pressure doesn't go to the RAVEs.

    The worst case scenario is when the pulse line splits before the one-way valve. This does two things, it allows the PTO side to lean way out, making it run like crap and eventually blowing it up if you continue to run it that way. Also the engine will not rev past 5K since the raves won't open up. These symptoms match what you are observing, so it is worth it to check it out good. Note that if the raves are sticky you will have these symptoms as well. The solenoid could be not working also. Lots of stuff to go wrong with the RAVEs, but it is an easy diagnosis and fix.

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