Power Head Gaskets

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  • September 25, 2017 at 2:39 pm #8313
    labrador-guy
    Participant

      US Member - 2 Years

      I noticed that the OMC 5 1/2 and the 7 1/2hp power head gaskets are slightly different. Anybody know why? Can they be used on either motor?

      thanks dale

      September 25, 2017 at 3:35 pm #65358
      frankr
      Participant

        US Member

        Should be the same, according to same year.

        September 25, 2017 at 6:34 pm #65367
        fleetwin
        Participant

          US Member - 2 Years

          What powerhead gaskets are you referring to?

          September 25, 2017 at 6:35 pm #65368
          1946zephyr
          Participant

            Yes, the lower units and exhaust housings are the same, year for year. Everything above the powerhead base gasket will differ though.
            The 7.5 was actually designed by Evinrude and the 5.5 was designed by Johnson. The two were not fully incorporated until 1956, when both nameplates went on ALL motors. Up untill 1956 the 3 and the big twin class were the only two motors shared through and through

            September 25, 2017 at 9:48 pm #65374
            chris-p
            Participant

              Here is the run down on Base Gaskets for the ’55 to ’58 5.5hp and 7.5hp OMCs. As you found, they can differ slightly. BE CAREFUL not to mix them up! Been there, done that.

              EVINRUDE

              MODEL YEAR HP PART #
              5512/5513/ ’56/ 5.5/ 304314
              5514/5515/ ’57/ 5.5/ 306205
              5516/5517/ ’58/ 5.5/ 306205
              5518/5519/ ’59/ 5.5/ 306205

              7518/7519/ ’55/ 7.5/ 303467
              7520/7521/ ’56/ 7.5/ 304314
              7522/7523/ ’57/ 7.5/ 304314
              7524/7525/ ’58/ 7.5/ 304314

              September 25, 2017 at 9:52 pm #65375
              chris-p
              Participant

                JOHNSON

                MODEL YEAR HP PART #
                CD12/ ’55/ 5.5/ 303467
                CD13/ ’56/ 5.5/ 304314
                CD14/ ’57/ 5.5/ 304314
                CD15/ ’58/ 5.5/ 304314
                CD16/ ’59/ 5.5/ 306205

                AD10/ ’56/ 7.5/ 304314
                AD11/ ’57/ 7.5/ 304314
                AD12/ ’58/ 7.5/ 304314

                September 25, 2017 at 10:19 pm #65376
                twostroke
                Participant

                  Thanks, Chris….I gotta’ CD-15 scattered and a buddy’s ’57 Evinrude 7.5 (that someone helpfully knocked the tag off…) and was wondering if I could mix/match some stuff outta’ my stash so he can go waterfowl hunting next weekend. This answers it…

                  Jim

                  I say "pardon me" a lot. I had a 20H, then raced open mod sleds.

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