68 20hp Johnson Replacement Gears

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  • April 2, 2015 at 6:28 pm #13226
    morelor
    Participant

      Hello All,

      I just wanted to give an update on what I have found out about my gears vs the gears in the 377877 gear set. I have learned that the gears included in the 377877 set are identical to my gears except for the fact that the gear teeth are angled in the opposite direction. My guess is that there is no way that they will work in my outboard due to the direction of the drive shaft rotation.

      Thank you to everyone who responded to this post! I really appreciate your help!

      April 2, 2015 at 6:52 pm #13229
      frankr
      Participant

        US Member

        ????? The drive shafts all rotate in the same direction. Offhand, I don’t remember the opposite angle of the teeth, but I don’t remember everything either.

        April 2, 2015 at 10:34 pm #13240
        fleetwin
        Participant

          US Member - 2 Years

          Did you check out marineengine.com? I’m pretty sure they have the original style forward gear and clutch dog in stock. There is no need to replace the pinion, unless it is damaged.

          April 2, 2015 at 11:46 pm #13243
          morelor
          Participant

            FrankR – Maybe it doesn’t make a difference, i’m not real sure. I assumed that the angle of the teeth would be related to drive shaft rotation direction but when it comes to boat motors i’m a novice at best so I really have no idea. 😀 I have pictures of the gears but I have no idea how to post pictures either 😆

            I thought about giving the 377877 gear set a shot but I was afraid that I might mess something up.

            fleetwin – Thanks for the info! I did check their price and it was $395.34 which is a lot cheaper than the quote I got from the dealer but that price still seems a little steep.

            April 3, 2015 at 12:42 am #13247
            phil-b
            Participant

              The 18/20/25 HP lineage "5 bolt" lower unit existed for a long time, it shouldn’t be hard to pick up a complete, used gearset if there is a possible issue with compatibility. 10HP engines before 1958 used the "5 bolt" gearcase, so that may be an additional source of parts.

              I seem to recall hearing (thru the grapevine no doubt) that they were machined as a set, and it’s better not to mix and match, but I’m sure lots of us do it (I know I have!) without tragic results.

              I don’t know much about "5 bolt" gearcase evolution, I know in the later 10HP "4 bolt" gearcase they switched from keyed to splined driveshaft and fewer, heavier teeth in mid 1960 (I think).

              April 3, 2015 at 1:05 am #13250
              fleetwin
              Participant

                US Member - 2 Years

                http://www.marineengine.com/parts/johns … n=Gearcase

                378079 fwd gear/bushing: $125- 5 in stock
                305191 clutch dog: $76.53- 4 in stock

                April 3, 2015 at 1:48 am #13252
                pappy
                Participant

                  US Member

                  Unfortunately this has been covered several times…….in the old forums.
                  You can repair the clutch dog and forward gear yourself if you would like to. With a Dremel tool and a fresh grinding bit. Save yourself a ton of money.
                  Take a file and cut the grinding bit face to around a 3-4 degree angle. Grind an undercut in the dog thrust face and the gear thrust face. Keep matching the gears together on the shaft to make sure you are cutting the gears equally. When done you will have a set that will not jump out of gear (that hit a log feeling). Also learn to make the proper adjustment of your gearcase shift mechanism so that you know you are fully bottomed out in forward gear. The extra drag you feel with you fingers will tell you the adjustment is correct.

                  April 3, 2015 at 5:06 pm #13280
                  morelor
                  Participant

                    Thanks for the info Pappy! I never really thought about trying to repair the gears but I guess I could give it a shot. Along with some rounded edges, I also have some lightly chipped teeth. Am I correct to assume that I would have to file the gears until the chips in the teeth are gone? Also, is OK to use the repaired gears long term or is it more of a temporary solution?

                    fleetwin – Thanks for the link! I was using the part number that the dealer used in their quote. FrankR had mentioned that the gear that I have been looking at is an upgraded gear with a roller thrust bearing. I assume there isn’t a problem with using 378079 fwd gear/bushing instead?

                    What kind of life expectancy should I expect from a good set of gears? This is my first outboard and the lower unit was pretty messed up when I got it so I really have no idea what to expect.

                    April 3, 2015 at 11:20 pm #13305
                    fleetwin
                    Participant

                      US Member - 2 Years

                      OK, well there is nothing wrong with using the original style parts. But, you mention "some lightly chipped teeth". Needless to say, if the pinion and reverse gears are chipped, replacement is the only option.
                      Why don’t you post some pictures to give us a better idea what condition your parts are in.

                      April 4, 2015 at 12:16 am #13308
                      chris-p
                      Participant

                        Put a wanted ad in the classifieds. There are a few members with NOS parts that are MUCH cheaper than what you have been quoted.

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