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18hp Fastwin lower unit seals

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  • 18hp Fastwin lower unit seals

    I have a 1969 18hp Fastwin model 18902B. I’ve owned it since 2012 with Little to no issues other than general maintenance. However I have never put a water pump in it, I have a new one and plan on doing it soon. But I’m wondering about trying to seal up the lower end. Ever since I’ve owned the motor the lower end oil is a little milky when I change it every year, never given me any issues but I’d like to try to fix it. I’ve already changed drain/fill plugs and sealing washers. Do I have to order all the seals and orings seperately or is there a “lower end seal kit”? Any of these seals or orings a usual culprit for leaking? Any special tools I will need?

  • #2
    The shift rod o-ring is often overlooked.


    • #3
      vintageoutboard.com has kits and most likely this site 's owner



      • #4
        thanks! anything to look out for, be aware of, or caution about doing this repair??


        • #5
          never done an 18hp myself but I would think they are all alike basically visit search UTUBES

          It may be simpler to just reload some wally mart oil in mid-season ......takes 5 minutes and done

          Last edited by Crosbyman; February 12th, 2019, 08:15 AM.


          • #6
            Originally posted by racerone View Post
            The shift rod o-ring is often overlooked.
            the oring your referring to is in the brass bushing correct?

            Crosbyman, i know that would be easier, however as long as Im taking it out to do the water pump, i might as well do it, im capable of the repair and if it doesnt totally seal up ill just go back to what i been doing and change the oil frequently


            • #7
              Some will argue ----But that shift rod O-ring can be replaced without removing the bushing!-----Resealing is easy and well worth doing.-----Have you looked at the price of new parts for these?-----These lower units ard gears were of a better design and durability that some new motors today.-----The gears / bushings with proper oil will just last and last.


              • #8
                this motor is in great shape, only thing ive ever done is replaced the head with a NOS because previous owner stripped a plug hole and tried to helicoil it. ive rebuilt the fuel pump a couple times, and rebuilt the carb a couple times, replaced the thermostat and points/cond when i first got it, and now just put a new set of points and cond in it. plugs and LU oil every year, only problem with it, i wish it were bigger! of course maybe its my fault for being to big!


                • #9
                  Look for a 28 or 33 HP model from 62 to 70.-----Just bigger motors with the same design concept.


                  • #10
                    i have searched for one of those, cant ever find one in a tiller steer. My problem is my boat has a wide beam, and since someone took all the control out and made it a tiller steer, I have everything in the back, me, start/deep cycle batt, trolling motor, and the fastwin. i put gas tank in middle of boat


                    • #11
                      Well I finally pulled the lower end and disassembled, on the bright side the water pump impeller wasn’t to bad, still plyable and in tact. Water pump housing is ok but does have some pitting inside it, not horrible but I’m thinking I should replace it. Found the lower unit leak, found a crack in lower skeg piece around the oil drain hole, now what? The motor runs to good and is to reliable to junk it


                      • #12


                        • #13
                          Test it first. With the l.u. off and empty, pump in a small amount of air with a hand pump (piece of rubber gasket material and an inflation needle works good in the fill or vent hole). Spray some soapy water around the suspected areas and look for bubbles. As mentioned above, the shift rod bushing is one of those areas.


                          • #14
                            just did similar work on my 5.5 when you go in to replace the various seals take time to wash down the lower half with carb cleaner inside and out apply a layer of Permatex STEEL WELD inside ...over the cracked area and outside area

                            smooth it best you can on the inside and outside surfaces...no need to put it on to thick

                            other option...

                            welding from the outside


                            • #15
                              Sign up today
                              i should have one for you for 10 bucks plus shipping