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Spark Plugs for a 1989 85 Force

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  • Spark Plugs for a 1989 85 Force

    I was recently told by a marine mechanic that I should switch from the Champion UL-18V surface gap plugs to a L77-JC4 plug with a .042 gap. He told me that "This plug fixes a problem with the newer unleaded fuels that the 89 year model engines cannot overcome otherwise. It vastly improves idling, low speed (eliminates the rumble & shudder) and burns cleaner at high speed. " However, I read a thread on this forum that says you should only use surface gap plugs because conventional gap plugs can burn a hole in the cylinder? I definitely don't want to do that. Which plugs should I be using? Can surface gap plugs perform adequately with today's fuel and will conventional gap plugs really burn a hole in the cylnder? Thanks.

  • #2
    Re: Spark Plugs for a 1989 85 Force

    Go and find another mechanic before that guy cost you lots of money. The surface gap plug is the only one specified by the manufacturer for your engine. Anything else is experimenting.

    Granted, there are speed shops for boats and cars and airplanes that develop their machines and processes separately from the manufacturer. However, these people have engineers, flow benches and CAD/CAM and have tested their product extensively.

    Somehow, I don't think your mechanic has the data to support his suggested changes.





    • #3
      Re: Spark Plugs for a 1989 85 Force

      The only time a plug "fixes a problem" is when you replace whatever is in your engine with a brand new Factory Specifed plug...
      It's a big blue watery road...

      1992 Arriva 1800 - Mercury V 150


      • #4
        Re: Spark Plugs for a 1989 85 Force

        Ditto! Get another mechanic!


        • #5
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          Re: Spark Plugs for a 1989 85 Force

          Thanks guys... he's not my mechanic, just someone who gave me some advice along the way. I'll use the surface gap plugs. Appreciate the input.