1958 Seahorse Fuel Mixture

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  • September 12, 2015 at 3:37 am #2506
    salsajedi
    Participant

      I am new here gents and was referred by a kind gentleman on the "IBoats" forum.

      I recently came into possession of a pair of 1958 Johnson Seahorse’s.
      One a 7.5 hp, the other a electric start 18 hp.

      What is the correct fuel mixture for these motors? There is a lot of conflicting information on the web regarding this.

      Thanks.

      September 12, 2015 at 3:40 am #23678
      mr-asa
      Participant

        I believe that those guys are 24:1

        September 12, 2015 at 4:01 am #23679
        chris-p
        Participant

          16:1 for the 7.5hp
          24:1 for the 18hp

          September 12, 2015 at 6:14 am #23682
          frankr
          Participant

            US MEMBER PAY BY CHECK

            I agree with Chris_P.

            September 12, 2015 at 2:05 pm #23686
            salsajedi
            Participant

              Thanks much for the answers fellas.
              I had a mechanic at the local marina tell me that they would run fine on 50:1 on account that today’s oil is so much better than what they had 50+ years ago.

              I’m glad I came here first.

              Thanks again.

              September 12, 2015 at 2:58 pm #23688
              wedgie
              Participant

                They will indeed run on 50:1…. but not for another 50 years like it will at 24:1 😉

                September 12, 2015 at 6:19 pm #23697
                chris-p
                Participant

                  Ask the mechanic if he will provide full warranty if any damage occurs running on that lean a mix! 🙂

                  Not all mechanics actually know what the heck they are talking about.

                  Little side story. Last week I had trouble with my Tower of Power, 115hp Merc. It would not run above a fast idle.

                  A Mercury Master Tech told me that it was because I had 87 octane in my tank!? Huh.

                  It ended up being the stator was shorted, but you get my point.

                  September 12, 2015 at 8:35 pm #23706
                  salsajedi
                  Participant

                    Should I use non oxygenated 92 octane or regular 87 octane gas?

                    Thanks guys.

                    September 12, 2015 at 8:40 pm #23707
                    Mumbles
                    Participant
                      quote Chris_P:

                      16:1 for the 7.5hp
                      24:1 for the 18hp


                      Exakery! The 5.5 and 7.5 horse motors have bronze sleeve type (friction) bearings on the crank and rods which need the extra oil while the ten horse use a combination of friction and needle/roller bearings while the eighteen horse and larger used needles and rollers throughout. Using a good brand of TCW III rated marine oil at the proper ratio instead of the motor oil suggested back in the fifties will help ensure the motor will still be running for your grandkids to enjoy!

                      September 12, 2015 at 8:42 pm #23708
                      chris-p
                      Participant

                        Plain old 87 octane is all you need, no matter what the master tech tells ya.

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