1955 25hp Johnson RDE-17 spark plugs

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  • April 30, 2021 at 7:29 am #237428
    Casey Parr
    Participant

      I currently have a set of champion J6C. I read someone runs a J8C which is supposed to be a little hotter and cuts the smoke down a little. People at my lake are getting a little grouchy at my well lubricated classic lol. It does lean up quite a bit after warm up. But at the dock area is where I’d like to improve a little. Any suggestions would be appreciated. Thanks!

      April 30, 2021 at 7:43 am #237430
      Fred Hickman
      Participant

        Burn HONDA HP2 two-stroke oil. I also burn 100 LL (Low Lead) gasoline. 100 LL is sold at local airports. It is 100 Octane gasoline with a small amount of lead added. This combination burns rather clean. I burn it in every two-stroke engine I own. Outboard motors, chainsaws, dirt bike, weed whackers, leaf blowers, yata, yata, yata. My 1957 Evinrude 18 HP Fastwin smokes little on this diet.

        April 30, 2021 at 8:05 am #237431
        crosbyman
        Participant

          Canada Member

          Evinrude xd-100 synt. oil $$$$ if you don’t cruise much……. is next to smokeless and comes with carbon guard 🙂

          Joining AOMCI has priviledges 🙂

          April 30, 2021 at 8:26 am #237432
          Casey Parr
          Participant

            Thanks! I was wondering about xd100! Do you still mix it 24:1? I read someone posted xd100 was harmful to carb engines, but I didn’t think he was right on that one lol. Seems to me full synthetic would be beneficial! Still wondering about the JC8 plugs tho. Don’t want to burn up a piston or run it to hot.

            April 30, 2021 at 10:08 am #237437
            crosbyman
            Participant

              Canada Member

              UNless opinions differ I would mix per engine guidlines …same for plugs

              xd100 hard on carbs…never hear of it but i eat crow on occasions

              Joining AOMCI has priviledges 🙂

              April 30, 2021 at 10:26 am #237438
              Casey Parr
              Participant

                That’s what I thought too! Thanks for the input. I’m headed for some xd100 and give ole Johnny a good swig. Let’s see how he pushes the 14ft alumacraft now! I’d be satisfied with just a little better 1st start out of the dock and see how that goes. I’ll test a small amount about 40:1 and a 24:1 separate mix in my tank at home today with my test prop and see how it goes.

                April 30, 2021 at 10:42 am #237439
                outbdnut2
                Participant

                  US Member

                  I don’t think changing spark plug heat range will make much, if any difference for smoke. The heat range is all about keeping the spark plug firing tip and insulator clean, keeping it warm enough to burn off deposits and cool enough to not self-destruct the plug, cracking the firing tip insulator, and causing pre-ignition. It has to do with how well the insulator for the firing tip is heat-sinked to the spark plug threads to conduct heat away from it. I would only use the hotter J8C if you mainly idle, like for trolling or lazily idling a pontoon around the lake. If you primarily run at higher speeds, the cooler J6C will be better.

                  If spark plug tip becomes too hot, glowing red, it can cause pre-ignition which is like hitting the piston with a hammer at the wrong time.
                  Dave

                  April 30, 2021 at 12:13 pm #237443
                  Casey Parr
                  Participant

                    Yeah I’ll stick with the J6C. That was very informative and detailed. I’m glad I ask a second opinion. I also saw J6J online, I thought those plugs were no longer available. I must have read something else on a different plug…Is the J6J about the same or better?

                    April 30, 2021 at 12:21 pm #237444
                    Casey Parr
                    Participant

                      Yeah I’ll stick with the J6C. That was very informative and detailed. I’m glad I ask a second opinion. I also saw J6J online, I thought those plugs were no longer available. I must have read something else on a different plug…Is the J6J about the same or better?

                      https://www.boats.net/product/johnson/0593871

                      April 30, 2021 at 12:48 pm #237447
                      Mumbles
                      Participant

                        You don’t need the J plugs when using TCW III oil. They were meant for when fuel was mixed using 30W motor oil.

                        • This reply was modified 4 years, 1 month ago by Mumbles.
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