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Thunderbolt 4 or 5 no knock sensor

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    Thunderbolt 4 or 5 no knock sensor

    Please help
    96 Bayliner 2665
    5.7
    won’t rev past 3100 rpm
    is there a limp mode on a Thunderbolt mod?


    #2
    This a new to you boat?
    Have you had successful runs at cruising speeds in the boat prior to this issue?
    is it stored in the water? Salt or lake/river?
    Does the reduced rpm happen at the dock in neutral (no load) or while trying to get up on plane (loaded) or??
    Dave
    Edmonds, WA
    "THE FIX"
    '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
    (.030 over-Vortec top end-part closed cooled)
    The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
    Misc. projects thread
    https://www.baylinerownersclub.org/f...56-gctid789773

    Comment


      #3
      TB IV does not have a knock sensor but the TBV does. Neither have a limp mode but the TBV will reduce the timing advance if knocking is detected. Limp mode is in th e 555 and newer systems.
      1997 Maxum 2400 SCR 5.7LX Bravo II

      Mike

      Comment


        #4
        Hi guys and thank you for quick responses
        I’ve owned this 2655 for 3 years
        always ran good for past 2 years
        on plane nice and quick
        this spring i had carb rebuilt and I did cap and rotor..new plugs and wires
        compression test was fair at 130-140 across all cylinders.
        I grounded proper wire and checked base timing and ignition mod is advancing properly
        double checked plug wires
        some oil fouling on plugs but it is a tired engine.
        i guess next is to check fuel line to mechanical pump.seems to be using a lot of fuel
        checked floatbowl overflow at 2500 rpm and nothing overflowing
        engine starts and idles fine
        just stops reving at 3200 rpm...almost makes plane
        thats why i was asking about limp mode
        now i can go back and concentrate on fuel delivery and spark
        any suggestions appreciated

        Comment


          #5
          You stated the ignition module is advancing as it should. I’d suspect poor fuel delivery also. Those mechanical pumps can be had for around $50, maybe time for a new one. Of course a fuel filter and take a peek at the ani symphony valve, I’ve read several posts about those becoming “sticky” causing poor fuel flow at higher rpm.
          Dave
          Edmonds, WA
          "THE FIX"
          '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
          (.030 over-Vortec top end-part closed cooled)
          The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
          Misc. projects thread
          https://www.baylinerownersclub.org/f...56-gctid789773

          Comment


            #6
            So you have the Thunderbolt V ignition? It was introduced mid 96’ and does require you to install a jumper wire to set base timing where the older TB IV does not.

            since it was running well prior to this work the issue must have been created by one of the things that was changed. You need to go back over each one at a time to find the culprit.
            1997 Maxum 2400 SCR 5.7LX Bravo II

            Mike

            Comment


              #7
              Thanks a ton Dave and Mike
              i pulled old hard fuel line off of anti siphon valve and found it empty...tells me bottom connection was leaking and probably sucking air into fuel pump...i am erring on the side of caution and replacing fuel pump-line and anti siphon valve
              Here in Canada our season is pretty short...no time to mess around..ha ha

              Comment


                #8
                I would do the same, glad you figured it out quickly.
                1997 Maxum 2400 SCR 5.7LX Bravo II

                Mike

                Comment

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