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  • GT-40 Problems

    I have a 98 SN, the Boat sat for approx 2 years because of health issues.
    I now have loud knock in the engine. Dealer says piston slap or bottom end??
    The boat has 750 hr's, never heard of too many GT-40 problems with these issues.
    Never ran low on oil, and never used a drop between changes. anyone heard of this before? Thanks

  • #2
    RE: GT-40 Problems

    piston slap will go away when the engine warms up usually. Bottom end will be a continuois knocking.

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    • #3
      yes, i always thought piston slap went away on warm-up. had it in 5.3 and 5.7 chev truck. I had never heard of it for 5.8 Ford , and never heard of too many bottom end problems with GT-40 with this many hr's. maybe something went on that first start-up after sitting for so long. and also the noise seems to get worse after use not get quieter as in piston slap. I thought it was a exhaust leak, but can't seem to locate, and don't smell any fumes under engine cover. anyone else ever heard or have these syptoms. Thanks

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      • #4
        piston slap is not going away, and you should ask Rob about issues on the gt-40 mot as he had to replace his two years ago because of a piston issue.

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        • #5
          Hate to say it but it sounds like a piston (s) issue for sure.

          From what I hear the 98-99 GT40 engines with the 290 ECM will burn pistons from a lean condition and fuel related issues so the fix is replace the engine, fuel pressure regulator, and replace the ECM to a 300 ECM.

          Have you done a Compression test or leak down test on the engine?
          Lack of proper planning on your part does not constitute an emergency on my part.

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          • #6
            Could you elaborate on the 98-99 GT-40 engines burning pistons? This is the first I have heard of it. I have a 98 with 270 hours and if there is something I can do now to prevent the burning of pistons I would like to do so. Have people been replacing the ECM's?

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            • #7
              its really hard to say but if it was ok when you last used it and noise was there when you fired it up after sitting for a long time there are a couple of different things that come to mind. how long have you ran it since sitting. my guess is a colasped lifter. i hope you would have changed the oil before trying to start it back up. it could take several minutes to pump the lifter back up. you also could have some stuck rings causing piston slap. but the lifter would be my best guess but it is very hard to tell without hearing it.
              4 main questions to you.

              1 did boat have any noise from engine last time you used it?

              2 did this nosie occur upon fist fire up after sitting or did you run it a little while then the noise pop up?

              3 how long has eng. run since you heard this noise.

              4 have you checked the oil pressure with a manual gauge?

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