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misfire above idle

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  • misfire above idle

    I have a 2002 F115TXRA outboard. I severly overloaded the boat for 8+hours, full throttle, top rpm was about 3800. boat never plained. At idle the cylinders all fire properly, no misfire. bring engine to a higher rpm, 1500+ and cyl.3 is completely dead, cyl.1 50% dead, cyl. 2+4 strong. Ran compression test all within specs. Replaced spark plugs, changed oil, replaced oil in lower unit. no metal found. pulled valve cover and checked valve clearance all in specs. any sugestions please. thinking about pulling trouble codes while running the engine.

  • #2
    what were the compression #s? I have never seen specs on compression
    Leak down tests are better indicators than compression
    How did you decide a cylinder was dead and half dead?
    Is there good spark at problem RPM?
    If compression and spark are good then check timing and if that is correct at problem RPM the you are left with fuel problem

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    • #3
      Outboards and fuel issues go hand in hand

      You need to do your own research to figure out problem, Mechanics can be waist of time. I just put fat oring around my quick connect and solved my issues. Fuel pump tired? Any leaks anywhere? What prop are you running, what boat, what alititude.

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