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84, 115 Mercury problems with #2 piston

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  • 84, 115 Mercury problems with #2 piston

    this motor is a inline 6 cyc. When running at full speed motor starts to ping, pull back on the speed pinging goes away. Take out the #2 spark plug and it has little pcs. of alum. from the piston on it. compression is 115 in all cyc. need all the help i can get thanks Ron

  • #2
    Re: 84, 115 Mercury problems with #2 piston

    can anyone help with this problem thanks

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    • #3
      Re: 84, 115 Mercury problems with #2 piston

      This is evidence of pre detonation. Check your timing. Also make sure that the motor is not getting to hot. Overheating also increases the temps inside the cylinder as well as not enough lubrication.

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      • #4
        Re: 84, 115 Mercury problems with #2 piston

        Before some says "predetonation? What's that?" I wanted to clarify that it's pre ignition, detonation and that I do know what I'm talking about. Conjunction, not misinformation.

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        • #5
          Re: 84, 115 Mercury problems with #2 piston

          Its preignition and due to either a bad idle stablizer or bia's circuit in switchbox
          When in doubt,Trim it out!!!
          Business Owner & Certifed Technician
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          • #6
            Re: 84, 115 Mercury problems with #2 piston

            thanks i took off the idle stablizer and put on two new switch boxs, it still does the same thing.

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            • #7
              Re: 84, 115 Mercury problems with #2 piston

              Did you check timing?

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              • #8
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                Re: 84, 115 Mercury problems with #2 piston

                no have not checked the timing, how would the timing change ???? no one has worked on this motor but me, i was told to set it at 19 deg. not 21 deg because of the gas now days ??? thanks for your help would like to find out what is causing this.

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