1975 Johnson 6hp powerhead

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  • July 5, 2021 at 6:39 pm #242017
    vasrf1980
    Participant

      Evening,

      I bought a 6hp Johnson this week model#6RL75R. I was told it ran but been sitting 25 years. So rebuilt carbs and ignition and free up some lock up linkage on the tiller. Got her started and wouldnt stay running. She was losing compression. So pulled pwr head and tore the motor apart. Pistons are both shot deep scoring on both. Cyclinder wall look goos to hone and install new piston and rings. Running into issues finding new pistons. Also looking for a pwr head to install. Anyone know what years are compatible? The part numbers for the crankcase and cyclinder assem change each year?
      Looking at a 1970 evinrude fisher model#6002B everything looks the same to include impellar shaft. Any input would be greatly appreciated.

      20210705_131115

      20210705_131109

      20210705_131048

      • This topic was modified 2 years, 9 months ago by Mumbles.
      July 5, 2021 at 6:53 pm #242023
      Mumbles
      Participant

        Any six horse powerhead from ’65 thru ’79 will be a direct bolt on. Driveshaft splines are the same, starters are the same, water passages are the same etc. The only major difference is in the ’77 – ’79 models which have Capacitor Discharge ignition instead of points style magneto systems.

        I don’t know why but piston scoring seems to be a common problem with these motors. Could be from wrong fuel mix, old fuel, overheating or any other thing. Where abouts are you located as I have at least a half dozen running and tested powerheads sitting on the shelf waiting for a new home.

        • This reply was modified 2 years, 9 months ago by Mumbles.
        July 5, 2021 at 7:30 pm #242031
        vasrf1980
        Participant

          Im located in ludowici, ga 31316.

          I had one vendor tell me his 1979 would not work because it has two water passages. One through exhaust and one through pee tube.

          How much would you want for the pwr head?

          July 6, 2021 at 8:45 am #242058
          fleetwin
          Participant

            US Member - 2 Years
            vasrf1980 wrote:

            Im located in ludowici, ga 31316.

            I had one vendor tell me his 1979 would not work because it has two water passages. One through exhaust and one through pee tube.

            How much would you want for the pwr head?

            I don’t think the 77 and later powerheads will fit your engine because the diameter of the mag plate pilot bushing is different…77 and later models use CDII ignition with different style mag plates.

            July 6, 2021 at 12:04 pm #242071
            Mumbles
            Participant

              Correct Fleetwin, the 77-79 powerheads can be used and will bolt on but they will need their original CD ignition systems with them because of the different boss size.

              July 6, 2021 at 12:09 pm #242072
              Mumbles
              Participant
                vasrf1980 wrote:

                Im located in ludowici, ga 31316.

                I had one vendor tell me his 1979 would not work because it has two water passages. One through exhaust and one through pee tube.

                How much would you want for the pwr head?

                The ’79 will work but you will have to either drill a hole in your lower pan for the tell tale or block it off.

                I’m located on the opposite end of the continent in Canada. A powerhead would be cheap but shipping costs would be the killer.

                July 6, 2021 at 1:29 pm #242078
                vasrf1980
                Participant

                  Gentleman,

                  Apprecaite all the help. I bought a 1970 6hp fisherman pwr head off a guy 3 hours south of me. Looks to be in good shape.

                  I verified that my ignition will work with it. Has all the same part numbers. Will get it mounted this week sometime.

                  Next question.

                  Is it worth it to rehone the cyclinder bore and drop new pistons in the old pwr head.

                  Pistons are $40-$60 with or without rings and hard to find.

                  If i have to bore it, i have the tools in my shop to bore it .010-.030 over. I saw there is a kit on amazon with rings, piston for .020 for $60. Then i would have to get pwr head gasket set $55 & headgasket $30.

                  So total rebuilt would be about $220.

                  Would it be worth it or just buy used pwr heads if compression is lost?

                  July 6, 2021 at 3:01 pm #242081
                  Mumbles
                  Participant

                    It would be easier and cheaper to just replace the powerhead than rebuilding it. I would also do a compression check on a powerhead before buying it. These motors do like to eat pistons for some reason.

                    August 30, 2021 at 7:28 pm #245824
                    vasrf1980
                    Participant

                      Thanks gentleman ya’ll are awesome. Powerhead worked great and fired right up. Just finished fixing up a 1970 9.5 and a 1971 9.5 evinruse and johnson. Now working on a 1953 10hp johnson and 1972 Merc thunderbolt. Jaut do this in my spare time. Loving bringing these old outboards back to life.

                      August 31, 2021 at 1:56 am #245840
                      JOHN HOLBIK
                      Participant

                        Vasrf80 Thanks for posting your results there is nothing more irritating then some one who leaves you hanging as to what the problem was.

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