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  1. #1
    javiert99's Avatar
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    787 misfire - diagnostic help needed

    This is a very odd misfire, with what it's doing I'm hoping someone ran into the situation before and can help me pinpoint.

    On the water it started when I was idling from the ramp, when I was getting ready to head out of the no wake I noticed the ski would not rev up and felt like it was either loaded up or missing (couldn't hear and pinpoint a misfire at the time). The thing I noticed was, if I turned the ski off, and right back on, the problem would immediately go away for about 3 seconds of normal WOT operation, then start to miss again. I did the off/on thing about 5 more times with the same results, and then finally the problem went away. About an hour into the day the problem came up again, lasted for about two minutes of me doing the off/on thing and finally it went away and we finished up our tank of gas and headed home.

    While flushing it on the trailer it began to do the exact same thing I could hear it alot more clearly on the trailer though and the engine stutters like it's hitting a rev limiter... it's clearly a lack of spark issue b/c my spark tester goes dim on *both* cylinders when it starts to happen.

    This started after my VTS boot cracked and flooded the ski last time I went out. I opened all the electrical boxes after it happened and through they were dry as far as I could tell. The front grey box is brand new according to the previous owner, and opening it up shows it I think... looks pristine in there, so I can't imagine it's not new. The ignition coil on the other hand had some rust on the bottom ground connections, so I cleaned that up and hooked it back up, but no difference. The only thing I can think of is maybe I missed some water at the rear box and screwed up the coil?

    Sorry if this is too long, tried to be thorough.


  2. #2
    steach's Avatar
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    Sounds like your voltage rectifier is going bad(at least I hope so cause they're cheap).

    The rectifier is in the grey box. It has three yellow wires and one red. To test it charge the battery, unplug the red wire and run the ski. If the problem goes away replace the rectifier. Caution: you will be running total loss and the battery will go down eventually.

    RQ (96xpss) showed me this one when my ski did the same thing. It's a common problem.

  3. #3
    javiert99's Avatar
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    I'll give that a shot in about 20 minutes if I can get the ski to repeat what it's doing.
    Last edited by javiert99; 10-22-2006 at 02:18 PM.

  4. #4
    javiert99's Avatar
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    Ok, went outside, the ski immediately after about 3 seconds started "misfiring" or whatever one can call it.

    Disconnected the red wire as you suggested and I was able to run the ski for about 15 seconds with no issues! woohoo

    Reconnected it, went back to misfiring.

    Gonna let it cool off some, then go outside and run it on the hose for a couple minutes with the rectifier unplugged to confirm!

    Thanks again dude, I'll go buy a rectifier on Monday.

    I'm surprised if this is "new" that it took a crap so quickly!

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