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!!No compression on cylinder, HELP!!

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  • !!No compression on cylinder, HELP!!

    Ok heres the situation, i recently purchased a 1997 sea doo gtx with the 787 motor 80 hrs, replaced motor mounts, lubed everything, rebuilt the carbs, and cranked it up last night, as of last night both cylinders were fine, 140psi-both.
    this morning took it out on the water for a trial run, and it was fine for about five minutes, ran up to about 6500-7000 rpm, then it shut off. Ok? so i cranked back up and kept going, babied it a little then let her open up again, this time ran up till about 5000 rpm would not go any more, after a few minutes stalled again, this occured three more times before it would not start again! i towed it back to shore with wifes ski and took it home! at home started digging into it, and voila, no compression - absolutely none on the front cylinder! Still at 140psi on the rear cylinder! wth? Any advise would be greatly appreciated!

  • #2
    Re: !!No compression on cylinder, HELP!!

    Sounds like a melted piston to me. My 580 did the exact same thing. Even down to the "it stalled and then fired right back up." Sounds like one of your carbs is running excessively lean, and melted a piston.

    The only thing to do is pull the head and have a look see.

    Keep in mind I've never seen a 787 and I have no idea what effect the power valve could have.

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    • #3
      Re: !!No compression on cylinder, HELP!!

      Originally posted by ttocs84
      Ok heres the situation, i recently purchased a 1997 sea doo gtx with the 787 motor 80 hrs, replaced motor mounts, lubed everything, rebuilt the carbs, and cranked it up last night, as of last night both cylinders were fine, 140psi-both.
      this morning took it out on the water for a trial run, and it was fine for about five minutes, ran up to about 6500-7000 rpm, then it shut off. Ok? so i cranked back up and kept going, babied it a little then let her open up again, this time ran up till about 5000 rpm would not go any more, after a few minutes stalled again, this occured three more times before it would not start again! i towed it back to shore with wifes ski and took it home! at home started digging into it, and voila, no compression - absolutely none on the front cylinder! Still at 140psi on the rear cylinder! wth? Any advise would be greatly appreciated!
      You cleaned the carbs and internal fuel filters? If so, did you also clean the fuel valve under the deck ( on off reserve valve).
      Bill O'Neal <br>
      WCM
      <a href="http://www.watercraftmagic.com"

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