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1957 18 hp Johnson Seahorse (electric start).

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  • 1957 18 hp Johnson Seahorse (electric start).

    Recently added this beauty to the collection. Placed it on the stand and it fired on the fourth pull. It did not pump any water so shut it down and ordered a new impeller from Iboats. Pulled the lower unit and the impeller looked almost new (no cracks/all tips in place). There was not a keyway on the impeller, but rather a metal "nub" on the drive shaft. Went ahead and replaced the impeller. The copper water line came off with the lower unit. Noticed the sharp end of the copper water line was pointed north and the square end was in the water pump. The bigger motors have the sharp end connected to the pump. Turned it around and attempted to replace the lower unit.

    1. With the new impeller, I can't rotate the drive shaft with my fingers. It feels too tight. Normal?
    2. I can't get the lower unit back on.

    What have I screwd up?

    thanks for any feedback/suggestions.

  • #2
    Re: 1957 18 hp Johnson Seahorse (electric start).

    The FD11 is a beauty motor, I have the same one but not electric start.

    It will be tight, but you should still be able to rotate the drive shaft in a CW rotation.

    How was the housing and plate? Be sure to ensure the water intake area is free of debris. Be sure that the water line does not pinch the grommet on either end of it when re installing or you will have restriced flow. Be sure that the vent hole on the housing is not clogged, nor is the drainage hole in the gearcase. Little critters love to nest in there. You did have the gearcase completely submerged beneath the water line when you ran it right? The pump needs to be under water.

    Did you change out the o ring at the top of the drive shaft? Re grease the splines? Dont get any grease on the TOP of the shaft, just on the splines. Sometimes you have to rotate the flywheel or prop while in gear to be able to slide the gearcase up. Dont pay attention really to which end of the water line is tapered, it will only fit one way. Does it line up after you flipped it?

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    • #3
      Re: 1957 18 hp Johnson Seahorse (electric start).

      I had her submerged pretty good.

      Housing and plate looked good. the intake had some greasy gunk in it. I'll double check the vent hole and switch the water line back around and may even put the old impeller back in. It didn't have an O ring. Need to get one and I'll try roatating the prop to she if she'll slip back in.

      do you grease up the new impeller?

      thanks for the advice.


      • #4
        Re: 1957 18 hp Johnson Seahorse (electric start).

        Dish soap works really well for putting the new impeller in. When they are new and tight and no lube they are very hard to turn.


        • #5
          Re: 1957 18 hp Johnson Seahorse (electric start).

          This may help.



          • #6
            Re: 1957 18 hp Johnson Seahorse (electric start).


            I got a new shaft O Ring from I Boats and was able to get the lower unit back on. In waiting for the O ring to arrive, I had the lower unit sitting on it's side. I noticed that it leaked out a bit of lower unit oil around the shift linkage seal. Can this be remedied?

            thanks for all your help.


            • #7
              Re: 1957 18 hp Johnson Seahorse (electric start).

              look for a thread currently on page 4 Titled Trying to Restore an 18 hp. Johnson by ccvolshdf...starting on page 2 of this thread he takes his gearcase apart and reseals it....this is where you are....a seal kit and some 3M 847 will be needed...directly to answer your question..there's a thick rubber oring that seals that shift rod shaft and it's held in place by and below the shift rod bushing which has to come out to replace the oring seal


              • #8
                Re: 1957 18 hp Johnson Seahorse (electric start).

                This may help.



                • #9
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                  Re: 1957 18 hp Johnson Seahorse (electric start).

                  HBW - Any chance you could post a picture of your starter and bracket from your motor. I would like to see how and where it is mounted.

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