1974 15hp Johnson, convert to 20" possible?

Home › Forum › Ask A Member › 1974 15hp Johnson, convert to 20" possible?

Viewing 8 posts - 1 through 8 (of 8 total)
  • Author
    Posts
  • July 6, 2017 at 1:20 pm #7557
    20mercman
    Participant

      US Member - 1 Year (includes $3 online payment fee)

      I have a really nice running 15hp Johnson that we picked up last fall and did some work on. This is a very nice running motor, however I don’t need another one, and I have a fellow that is asking me for a motor for sale. I really want to send this Johnson down the road to a good home as it is a great fishing motor. The problem is that it is a 15" transom motor. Can these be converted to long shaft, and if so, any ideas of where I would be able to find a kit for one?

      Thanks!

      Steve

      July 6, 2017 at 2:22 pm #61096
      frankr
      Participant

        US Member - 1 Year (includes $3 online payment fee)

        Long shaft kit was part # 386710, replaced by 392002, listed as NLA

        July 6, 2017 at 3:58 pm #61105
        outbdnut2
        Participant

          US Member - 1 Year (includes $3 online payment fee)

          Maybe you can find a dead donor motor cheap. The 9.9s and 15s of that era should give you the short driveshaft and shiftrod you need. Also the water tube, but you can easily shorten that if necessary.
          Dave

          July 6, 2017 at 4:41 pm #61113
          dougs-outboards
          Participant

            Dave I think it’s already a short shaft, he’s wanting it to be a long shaft, so needs long shaft parts… sadly I have none to offer.

            Yes a dead donor motor would be the ticket. Don’t pay over $50 for it tho.

            July 6, 2017 at 5:04 pm #61116
            outbdnut2
            Participant

              US Member - 1 Year (includes $3 online payment fee)
              quote Dougs Outboards:

              Dave I think it’s already a short shaft, he’s wanting it to be a long shaft, so needs long shaft parts… sadly I have none to offer.

              Yes a dead donor motor would be the ticket. Don’t pay over $50 for it tho.

              Opps – must have had a senior moment – anyway a donor 9.9 or 15 would still work.
              Dave

              July 6, 2017 at 5:41 pm #61120
              fleetwin
              Participant

                US Member - 2 Years

                This is not a tough swap to make at all…
                The good news is that the driveshaft pulls right up and out of the gearcase, so it swaps easily. Be sure to get a driveshaft with an oring groove on the upper splines, don’t use the non-oring driveshafts. I think there was some sort of change to the lower splines on the early engines, so be sure those match completely as well.
                Used gearcase extensions are plentiful and affordable. Be sure to get the white plastic tube/extension seal as well. These are usually just found stuck into the used extensions…
                The shift rod simply unthreads up and out and can be swapped easily as well. Be sure to thread the longer shift rod all the way down/bottomed out, then back it off just slightly so the bend is facing forward for proper adjustment. The shift rod cavity tends to get plugged with dirt/sludge, there is a drain hole down there but it is usually plugged. You will want to clean this area well prior to removing the original shift rod to ensure none of the sludge goes down inside the gearcase when the original shift rod is removed. Coat the lower portion of the longer shift rod generously with grease prior to threading it in to help lubricate the shift rod oring for good sealing.
                The powerhead would have to be pulled in order to change the water tube, but I’m pretty sure the make a 5" extension for the short water tube that seals with an oring that can be added to the original short water tube. This way, the powerhead does not need to be removed…
                Here is the part number for the extension:
                http://www.marineengine.com/newparts/pa … OMC0320025
                Not cheap, but definitely worth its price to avoid pulling the powerhead…
                Don

                July 7, 2017 at 6:02 am #61165
                PugetSoundBoater
                Participant

                  The 5" longer water tube as Fleetwin mentioned is the way to go. Be sure it has the o ring PN #020893 that fits in the notch in the tube where it fits over your existing water tube for a good seal. I can’t remember if it came with the water tube extension 320025 when i bought it.

                  "Some people want to know how a watch works, others just want to know what time it is"
                  Robbie Robertson

                  July 12, 2017 at 7:34 pm #61485
                  joellerich
                  Participant

                    US Member - 1 Year (includes $3 online payment fee)

                    I have a complete kit to convert a short shaft engine to long shaft. The parts came from a 9.9hp Johnson MQ series. If interested let me know. I can send pictures. I think it would fit your engine, but am not certain. You may have to post the question to some of the experts. I will be at Tomahawk August 3 and 4

                    John john.oellerich@q.com.

                  • Author
                    Posts
                  Viewing 8 posts - 1 through 8 (of 8 total)
                  • You must be logged in to reply to this topic.