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OMC Stringer transom seal replacement?

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  • OMC Stringer transom seal replacement?

    Got the new seal and got the old one off.
    What should I use as a sealant between the seal and the intermediate housing?
    I assume a bit of RTV gasket maker or similar would be fine to seal the rubber seal to the transom but is the seal glued to the intermediate housing to prevent if from coming loose? I assume loose could mean sinking.

  • #2
    Re: OMC Stringer transom seal replacement?

    The factory never used a sealant on the intermediate housing or on the transom. On replacing the boot, make sure that you thoroughly clean the flange on the IH housing, then use a slow drying sealant that will let you rotate the boot to line up with the screw holes in the transom. You did not mention it but I assume you have the large band clamp to anchor the boot to the IH housing. Once you get the holes lined up, tighten the clamp. Then apply a thin bead of the sealant to the transom, using the screw holes as a guide for the bead. Then run the screws in. No need to over tighten them, just enough to firmly press the boot to the transom.


    • #3
      Re: OMC Stringer transom seal replacement?

      My son is a mechanic. He suggests "the right stuff" as he says it is tackier and less slippery than most silicon gasket makers.
      When I took it off, I literally had to cut it off and it appeared to have a light colored rubbery sealant on it on the intermediate housing.
      I wondered if there was a "factory" goop that was recommended. My manual says nothing about replacing this seal that I can find.

      I maybe need to change the trim adjustment as the seal has to be stretched at the top to get to the screw holes. Tilting the front of the motor up may help to align it a bit better.

      Someone on here suggested that the rear engine mounts can settle and that can cause issues with the seal. Any advice on how to tell if the engine has settled? Just look to see if the intermediate housing appears to be reasonably centered in the hole?


      • #4
        Re: OMC Stringer transom seal replacement?

        Maybe someone replaced the boot once before? I bought my boat new in 1975 and pulled the motor and outdrive assy in 2006 to replace the floor and redo the mount stringers. When I unscrewed the boot from the transom, there was absolutely no sealant/adhesive. When I removed the boot from the IH housing, there was absolutely no sealant/adhesive there either. I cleaned up the IH, repainted it, and reinstalled it with the same boot. I am not 100% positive what sealant I did use but it was most likely Gasgacinch, which is a very light adhesive. No reason the the 'right stuff' would not work but I think it is overkill. You do, however, want the ability to rotate the boot once you have it on the IH because you never get it on in the exact right location, to line up with the holes in the transom. I actually marked my boot and IH housing with pink chalk to make the lining up easier but I still had to rotate the boot a little bit once I got it on.

        I think if your mounts had settled you would see substantial evidence in the fiberglass covering them. I've seen them rot to where they would not hold lag bolts but there was no settling. Just make sure that you have your front mounts as low as you can go. That will raise the IH mounting flange in relation to the transom opening.


        • #5
          Re: OMC Stringer transom seal replacement?

          Thanks much for your input. This is new to me.

          Very little doubt but that it has been replaced before. This is in a 1973 Starcraft Holiday 18 - so an aluminum boat.
          There is more space at the top of the opening in the transom than there is at the bottom. It does not appear to be centered in that way. Side to side is pretty good.
          Looking at it, I thought it would likely be best if the IH was angled to match the transom. Right now, the front of the motor is down too much and I have an issue with the trim motor so I cannot readily crank it back up.


          • #6
            Re: OMC Stringer transom seal replacement?

            My boat does not have trim. I went out to compare my vertical alignment with the description of yours. My IH is much more centered than you describe yours as being. My IH is approx. 3 1/2 " from the boot flange to the bottom edge of the boot, on the bottom and about 2 3/4" from the IH flange to the edge of the boot, on the top. Also for you to compare, with my outdrive in the down position, I took a straight edge and laid it along the (the term escapes me) plate just above the prop. I slid it back till it touched the transom. It contacted the transom 1/2" above the bottom of the hull.

            Earlier research on the subject shows this to be within the recommended dimensions of the relationship of that plate to the bottom of the hull.

            Based on my description and depending on the height of your outdrive in relation to the bottom of your hull, you could make some motormount pads to raise your assembly up. Maybe your assy is at the right height and they just cut the hole in the transom too high? It'd be interesting to hear.

            btw, my transom has a backward slant so that the top of my IH flange is close to even with the transom at that point but the flange sticks out past the transom, at the bottom, approximately an inch.


            • #7
              Re: OMC Stringer transom seal replacement?

              Thanks for taking the time to measure.
              I will check my boat this evening and maybe take a photo or two to post.
              The leg is off while I mess about with the seal so not easy to check the alignment of the cavitation plate with the bottom of the hull right now.


              • #8
                Re: OMC Stringer transom seal replacement?

                It is in. Fit nicely. No issues. Decided to try it without any sealant and see if it leaks. If not, then no problem.
                However, I had to put it in upside down in order for it to fit nicely. The top and bottom marks on the seal are reversed.
                Not sure what that means but it seemed to work better. I did not have to stretch the rubber as I did if I had it right side up.
                I had about 2 3/4" of opening on the top between the edge of the opening and the edge fo the IH where the band clamp fits and about 1 1/4" on the bottom so not an equal amount at all. I noticed that the rubber was wider on the bottom so I reversed it and everything seemed to fall into place. I did measure the distance from the pivot points to the cavitation plate on the leg and on the IH and it appeared that the drive was sitting about right with the cavitation plate just above the bottom of the hull.
                I guess time will tell if this was the right thing to do but it surely seemed to be at this point in time.


                • #9
                  Re: OMC Stringer transom seal replacement?

                  Hmmm, it just occurred to me that you never said what year your drive was. Mine was a '75 electric shift intermediate with a '79 hydro-mechanical drive mated to it. The electric shift boot was a different shape than the later hydro mech and full mech drives. As such, if you have a later IH and drive, my dimensions were not applicable.

                  I think if all your mating surfaces were smooth and clean, you won't have a problem with not using a sealant/adhesive.


                  • #10
                    Re: OMC Stringer transom seal replacement?

                    The boat is a 1973 Starcraft Holiday - 18 footer -Aluminum.
                    The drive is an electric shift stringer and the motor and drive are likely original.
                    I acquired it in late summer 2010 but have never had it in the water yet.
                    I have had the engine running without the drive attached, on the hose.
                    I am about to put the drive back on and find out if it is in reasonable shape. The motor starts up and idles nice.
                    We shall see how it does in the water. Got my fingers crossed.


                    • #11
                      Re: OMC Stringer transom seal replacement?

                      T'would be the same boot that I have, then. Good luck with it. Do you know that the drive shifts? Did you change all the fluids?


                      • #12
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                        Re: OMC Stringer transom seal replacement?

                        Not quite there yet.
                        Rained here this evening or I would have had the leg bolted on by now.
                        Going to change fluids in the leg.