4 of 8 cylinders not firing? GT-40, 02' SAN-- Please Help!

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  • claytons
    • Apr 2006
    • 7

    • Austin, TX


    4 of 8 cylinders not firing? GT-40, 02' SAN-- Please Help!

    I have a 2002 Super Air Nautique with the Ford 5.8L (351)HO GT-40 with 1200 hours on it . I replace my spark plugs annually and oil every 125 hours, and I did so 2 days ago. When i started the boat it was idling very rough. i.e. jumping from 600 to 650 to 700 rpm. I removed the plugs, checked the gaps, replaced the plugs, and checked the firing order. Then I restarted the problem persisted; at this point I drove the boat -- the engine was vibrating heavily and there was loss of power when accelerating. I removed the plugs immediately after this, i found plugs 3 and 4 to be wet and plugs 6 and 8 with a little oil on them. All the others where bone dry. At this point I replaced my spark plug wires, distributor cap, rotor and all eight plugs; Still the same problem. How can this be? Maybe the coil? Please help!
  • richard
    Senior Member of PLANETNAUTIQUE
    • Feb 2005
    • 406

    • HK


    #2
    wet spark plug

    You very like got the problem leaking manifold/riser leak, if your boat 1200hr didn't change the manifold/riser ,change it will solve the problem.since your engine mix water,you need to drain and change few time to clear it.

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    • nms1991
      Senior Member of PLANETNAUTIQUE
      • Apr 2004
      • 477

      • Unknown


      #3
      RE: wet spark plug

      Not to question your ability but check your oil level. Is the check engine lighton the dash?

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      • farmerandy
        • May 2006
        • 13

        • Boyd Texas


        #4
        See my post titled GT-40 Over Temp Indication for the stuff I had to do if it is your riser - manifold interface leaking water into the exhaust gas stream.

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