1936 Johnson A-80 4.5 hp Spark Plugs?

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  • November 8, 2017 at 10:59 pm #8629
    Buccaneer
    Participant

      US Member

      My subject motor had AC 85M spark plugs in it.
      They’re 18 mm, and "shorties", that is not the "reach",
      but total length.
      Can’t find in any "specs" the recommended plug.
      I don’t remember ever seeing the short 18 mm plugs either.
      I believe I could use full length plugs and not have
      an arcing problem. Looks like there would be about 3/8"
      clearance from the plug nut to the spark plug door.
      Shorties would be nice though if they still make them.
      Thanks!

      Prepare to be boarded!

      November 8, 2017 at 11:04 pm #67156
      RICHARD A. WHITE
      Participant

        Lifetime Member

        The Old Outboard Book Volume 3 shows a 5MJ originally gapped at .03, That plug in the same book was replaced with a D9J

        So did some searching and found this:

        http://www.sparkplug-crossreference.com … AMP_PN/D9J

        http://www.richardsoutboardtools.com
        classicomctools@gmail.com

        November 9, 2017 at 12:55 am #67161
        Buccaneer
        Participant

          US Member

          Richard, thanks for your time and effort!
          Wonder if any of those "alternate" plugs
          were of the "short" variety…… will have
          to research that.
          Thanks!

          Prepare to be boarded!

          November 9, 2017 at 1:21 pm #67173
          eltoquad
          Participant

            US Member

            I have some NOS M85 A.C. plugs if interested PM me. They are not shorties and not even sure if the same heat range but I run them in several of my ’30’s Eltos.

            November 9, 2017 at 3:47 pm #67174
            rapier
            Participant

              The NGK AB6 is a conventional length plug.

              November 9, 2017 at 5:16 pm #67175
              Buccaneer
              Participant

                US Member

                Thanks for the replies. I can get the Champion D-9’s
                in town, and have some Autolite 3116, copper core,
                non-resistor, coming. Sounds like they may be
                too hot on the heat range though.

                Prepare to be boarded!

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