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Loss of power, then backfiring after over an hour of hard travel underway-gctid825958

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    Loss of power, then backfiring after over an hour of hard travel underway-gctid825958

    Recently purchased a 2005 Bayliner 245 with a 5 litre Mercruiser and Alpha 1 leg. The motor was recently rebuilt by the previous owner due to improper storage over winter. The boat has very little usage, however symptoms have been showing up, most of which we solved at certified Merc dealer where the rebuild was done. There is 1 reoccurring symptom that has the mechanics baffled. After being underway, and keeping its comfortable cruising speed of 25 knots and the RPMs at around 3800 for over an hour, there is a noticeable loss of power, followed by backfiring through the carburetor. When this starts to happen, I reduce the throttle, and the engine remains idling, however it has no power and will continue to backfire if I continue to go forward. The mechanics have taken it out on several sea trials, and have given it a clean bill of health every time, but they haven't taken it out long enough for this symptom to appear. The symptom doesn't show up until after an hour. We have to wait for the engine to cool down for several hours, and then we can get underway again. As a blind attempt, the mechanical fuel pump was changed out, however that was just a guess. The problem still remains. The fuel has been repeatedly inspected for any turbidity or water. None has been found. The mechanics are just guessing at this point. Has anyone had any experience with this, and/or any solutions to this problem? Thanks Dave

    #2
    Welcome!

    Please fill out your signature so we know more about the boat and where you boat! It helps us help you!!

    Ck the fuel system, fuel filter, pump and carb!

    Sounds like it is leaning out !

    Remove the fuel filter and pour the contents into a glass jar, let it set over night , if there is water in there you well see it at the bottom of the jar!

    Cut open the filter to see if there is any crud in it! If so you may have to drain the tank !

    Don
    1995 Maxum 2400 SCR LUNA DE MIEL
    1988 Bayliner 2455 (sold)
    1976 Tahiti 16.5 I/O (sold)
    10 ft livingston (lost in fire )
    1987 18ft. Seaswirl cuddy (lost in fire)
    "Is it better to be on a boat thinking about God, or be in church thinking about boating?"

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      #3
      Welcome! Please add your boat information and where you are to your signature.

      I had a similar reaction, though very short duration, when doing a full throttle test on my last boat. It had a pair of 2001 4.3's, with 4bbl carburetors and counter rotating alphas. When I got the rpms to 4800, one of the props caught a bit of air and the overrev limiter kicked in. I thought I blew the engine up. Of course I brought everything to a stop, then had to restart both engines. The limiter reset and I was off again, able to cruise at the normal 3450. I'm thinking your limiter is engaging due to a buildup of heat. It's just a guess, but may help.
      P/C Pete
      Edmonds Yacht Club (Commodore 1993)
      1988 3818 "GLAUBEN”
      Hino EH700 175 Onan MDKD Genset
      MMSI 367770440

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        #4
        Check to see if the fuel tank vent is clogged. Next time it happens loosen the gas cap to see if it recovers.
        1997 Maxum 2400 SCR 5.7LX Bravo II

        Mike

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