ideas on gear case seal replacement

Hi All.

I drained the gear lube on my 81 Johnson v4 90 hp and just under a quarter of a cup of water was the first thing to come out. Using my home made pressure tester the gear case did fine with around 10psi for just under ten minutes.

i have no way to vacuum test and i beleve from reading other posts that a warm gear case will pull water in when cooling in the water.

There's a chance it's the seals on the filling and drain plugs for the gear case, but as it's now winter over here and as the seals are now possibly 32 years old, i thought i would look into replacing them, which was also suggested routine maintenance previously on this site.

There were very few fine iron filings on the magnetic drain plug, but there were no chunks of steel or heavy meal filings in the drained gear case oil. The gear case also goes into and out of gear very smoothly (smoother than my mates 90's mercs or mariners) so i am pretty sure the internals are all good.

I'm worried about taking the whole gear case apart to replace these seals due to the complexity and precision of the gear case that i am looking at ways of replacing the sals without dismantling the entire gear case.

from what i an see there are three main seals. Two where the prop shaft exits at the front of the gear case. Two where the drive shaft enters the gear cas, under the water pump and 1 where the gear shaft enters the gear case.

I found a method by a guy who did two yamaha gear cases, by drilling and pulling the seals with screws and then pushing the new ones in using a type of socket on youtube. In his method he only removed the seals and none of the circlipe and other retaining bolts.

Can anyone give me some guidance on the easiest and simpleest way to do this kind of work with minimal specialized tools and complexity?

ps i did put new lube in while i'm deciding what to do so it's not standing empty and wet.

Thanks as usual.

very fine metal dust or grit is normal wear so no worries there. as for the seals being replaced without pulling the gearcase and lower apart I don't think it can be done. if ur even somewhat mechanicaly inclined buy a service manual and its not that hard. I used a wooden dowel to remove and put back in my driveshaft seals and it worked fine. not sure about ur gearcase being that its a one piece and mine(25hp 1980) is 2 pieces and comes apart so all that stuff is easily accessible...I believe you need a special tool to remove ur propshaft/gears etc....good luck!

This work is actually very simple.-----No need to be afraid of taking this apart.----Get a seal kit and replace every item !

Thanks for the comments and advice. I have decided to give this a full go.
I'm unable to find a kit on this site. can someone tell what i should be getting as individual parts or where i can get a kit please?

One of the other things i noticed while looking at the individual parts on this site is that many of them have equivalent parts from Mercury Marine. Does that mean that i could the parts from Mercury using the Merc part numbers given?

The reason i ask is that i normally have my parts shipped in from the US as they are crazy expensive down here, but Mercs are far more common and the parts are priced a lot better.

Thanks again

The -----Siera ----catalogue lists a seal kit.----Find it on this site !

Thank you racerone. Once again I bow to your experience and knowledge. Siera kit 18-2692. On order. I will let you all know when I get the parts and I will document the repair process for anyone else who may need this in the future. Thanks again

Just a bit of a warning....or a word to let you know to be prepared....that repair is not a piece of cake. The propshaft bearing carrier can be, and often is, frozen in the LU case. It takes a puller to get even the "non-frozen" ones out. Granted, you can make one, but expect to use a puller to get the bearing carrier out. Heat too, for that matter. And even tho this may sound minor to some, the shift shaft o-ring can be a real bear to install, to a non-skilled mechanic.

The shift shaft O-ring simply pulls out of the housing and a new one is pushed in --No hammers , muttering required.--------The bushing does not need to be removed at all !!

I know how to do it. Does he?

Hi Daselbee and racerone. Other than the water pump, gear lube and prop the gear case is foreign to me.
i've ordred the seal kit and it will about two weeks before it arrives. I'm going to use that time to read up as much as i can in my manual and on the various forums. I only want to remove what i have to.

I have a bearing puller that i use for my wheel bearings on the trailer, but if possible i would like to avoid pulling anything i don't have to and especially anything that requires heat.
I am an average mechanic, but kt's a hobby for me. i am by no means highly experienced.

I have a few weeks to do this so i'm in no rush. I was thinking that i might begin the dismantling in the next few days, but i'm concerned about having the parts on my bench exposed to air and dust while i wait for the spares, so i think the best course of action, like usual, is to await the spares arrival and then begin, hopefully with a good theoretical knowledge of the process.

i'll be reaching out in the next few days to check my understanding on what I've read.
Thanks Again

Unless this gearcase is a " salt water mess " then this work is elegantly simple.------Shift rod O-ring seal is one of the easiest to replace !!

Hi From what i am reading it seems pretty simple.

Looks like i have to remove the prop shaft bearing housing to replace the o ring at the rear of the bearing housing. The prop shaft bearing housing appears to be held in by two 4 screws attached to a retainer plate. I remove these bolts and then use the puller to gently remove the bearing housing from the prop shaft, but the prop shaft is not removed. From what i can see this as far as i need to go on the prop shaft section. The motor has never been in salt water so corrosion should be minimal.

I remove the drive shaft bearing housing from under the water pump and then remove the shift rod cover.

i then remove seals from front and o ring from rear of propmshaft bearing housing, seals from drive bearing housing, gasket and o ring from under shift rod cover and replace all one by one. Shift shaft and drive shaft are not removed for this.

assembly is then the reverse process.

will take photo's as i go.

You are starting to understand how simple it is.----Just nothhing to it !

Racerone...cmon down to Mims, FL and work on the 1979 140 I just did. Hammers and muttering are the very least of it. Torches, broken bolts, frozen bearing carriers, bent and broken pullers....even had to cut a bearing carrier out one time...sawzall. Rotted DS bearing housings, impellers stuck to the driveshaft, driveshafts and propshafts with grooves in them that will NEVER seal back up....it ain't as easy as you make it sound. This job is absolutely one of the worst jobs in working on these motors. IF the owners would service their motors with a WP every year, then they would probably come apart better. I certainly hope the OPs job goes easily for him. He DOES DESERVE to know the pitfalls tho.