Do you Apply Sealant to Pressed in Seals in OMC Gearcases?

[Evan VanBeelen]

Hello, I am working on rebuilding my first outboard gearcase on a 1957 Evinrude 5.5HP because the seals were leaking. I’ve watched a number of videos on putting them back together and how to apply sealant around the spaghetti seal, but I am getting mixed signals on the round/cylindrical seals with a rubber inner surface and a metal outer surface that press into the housings. I’ve seen some videos where they have applied a thin layer of sealant on the outer diameter of the metal seal case and others where they haven’t.

It seems to me that you would only need to press the seal in and then apply a small amount of triple-guard grease to the inner seal surface and call it a day, but I’m not sure. My concern would be with getting the sealant in unintended places and causing more problems than good. Any other seals I’ve ever replaced like wheel bearing seals, I have never applied a sealant to this outer surface, but obviously outboards are a bit different due to the fact that they are fully submerged.

Is it generally advised to apply sealant to those outer surfaces where the seal presses into the case, or not?

Any other advice is also greatly appreciated! I’ve got two 57 5.5HP Evinrudes, and two late-60’s 9.5 HP Evinrude’s that I have picked up and am replacing the lower unit seals in all of them. I’m also rebuilding carbs and going through the ignition systems, but I’ve been through those before.

[bobw]

I have typically applied a gasket sealer on the exterior surface of the oil seals when resealing a gearcase. I don’t know that it’s absolutely necessary but I’ve always done it. When you apply the sealer around the seal and then drive it into the bore, a lot of the sealer gets pushed outward anyway but that kind of seals the joint between the seal and the bore so that’s good enough for me

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[crosbyman]

I  have use aviation sealer  (847 expensive and not available) to seal the GC.  follow the  utbes   don’t forget to do a pressure test  to confirm the job is 100%

to best maintain your oldies this book covers everything you need

https://watercraftmanuals.com/outboard/johnson/manuals/johnson-302231.htm

 

check that silly shock absorber   for proper size   6&11/16″ max.

otherwise you will  have to do it again .

Vidéos Bing

Joining AOMCI has priviledges 🙂

[fleetwin]

Well, it is one thing talking about seals being pressed into housing in the factory.  New perfect surfaces, no need for sealer between the metal seal casing and housing.   None of us are working with new engines.  Keep in mind that the aluminum housings oftentimes get marred/scratched/grooved while attempting to remove those seals out of those housings.  So, I always put a very fine film of OMC gasket sealer on the outer diameter of the metal seal housing during assembly.  And yes, most of this get pushed up and kind of just rests on top of the outer diameter of the seal, so you sure want to apply it sparingly.

I am constantly frustrated when folks seem to believe that resealing one of these gearcases is simple/straight forward.  Have you ever tried to get those seals out?  Use some honkin seal puller/pry bar set up, and you will quickly destroy/gouge the delicate aluminum housing.  These seals usually have a pretty tight interference fit into the housings as well.

The shift rod oring/seal offers its own challenges, pretty tough to remove/install it without the special tool.  And, if you do coerce the oring out of the cavity without removing the bushing, chances are slim you will get the new oring back inside there fitting properly.

And lastly, there is the debate about the lovely gearcase/skeg “spaghetti seal”.   Generally speaking,  the spaghetti seal should not require any sealer, except around the ends where it butts up against the prop shaft bushing/seal housing.  I use a thin layer of the dreaded type M/847 mainly underneath the spaghetti seal because it dries quickly and is super strong.  This spaghetti seal tends to want to pop out of the machined grooves, especially during skeg installation.   So, I rely on the type M/847 as a glue mostly, to make sure that darn spaghetti seal stays in place.  The ends of the spaghetti seal must be properly trimmed as well.    Another design flaw on these gearcases is that the skeg retaining screws are “inside” the spaghetti seal and pretty much rely on tight interference fit between the screw head and the skeg in order for these areas to seal properly.  So, if the aluminum surfaces underneath the screws are damaged/not flat/gouged, another water leak will be introduced.  I’m guessing OMC wanted to save money on specialized/precise fitting spaghetti seal that surrounded the retaining screws.  And once again, parts assembled at the factory are brand new, imperfections/damaged surfaces are unlikely.   I suppose a less expensive solution would have been to use retaining screws with grooves for oring…..Kind of like the pivot pin screws used on later models.

It amazes me how many people assemble these things and don’t do a pressure test.  Keep in mind, there is a zero tolerance for any leaks.  These things are not like car engines, there is no “dipstick” to check oil level/condition.  And, keep in mind, that oil doesn’t just leak out, it is usually replaced by water inside the gearcase… If a car engine drips a bit of oil, no biggy, just keep an eye on it, and top it off every once in awhile, not really possible on one of these gearcases.   I would agree that most could probably get one of these units back together and shifting OK, but sealed up properly??  Highly doubt it.   In most cases, the amateur was probably better off with the milky gearcase he started with than the gearcase full of water he finds after resealing.

Now, consider the upset when you have carefully done everything to the best of your ability, and find a leak during the pressure test.  Now, most likely the gearcase have to come apart again, meaning new spaghetti seal/oring.  Imagine the thrill of having to clean all those mating surfaces up again, especially trying to clean the sealer out of the groove in the skeg.

1 user thanked author for this post.

bob-d

[crosbyman]

and then again   in  E.wawrzynialak “CHEAP OUTBOARDS”  if the leak  does not seems ” to bad”  one can simply  flush and refill with  new cheap GC oil….

“In most cases, the amateur was probably better off with the milky gearcase he started with” …Fleetwin

but if your  are going to become addicted to oldies  … practice makes perfect,

the shift rod o-ring is tricky but easy to do  (check utubes)  on tapping and extracting that brass plug above the oring.

Joining AOMCI has priviledges 🙂

[outbdnut2]

Hey Fleetwin – Good summary of what most of us hobby guys have learned over the years by trial and error!

When you talk about water replacing gear oil and no dipstick,  it made me think of my 1996 ski boat with a MerCruiser Inboard/outboard drive.  It has a tube coming up from the top of the gearcase,  to a plastic  see-through reservoir with a filler cap high up in the engine compartment.  In most cases, as gear oil leaks out, it gets replaced by more gear oil due to the static pressure from to the height of the reservoir above it, and I can see if there is a problem if I have to add often, and it’s an easy add, just pouring it in.  This would be a great thing to have on outboards, especially bigger ones.  It’s not perfect though.  I had the gearcase driveshaft seals dislodge – there are two of them pressed in and both came loose, and were crooked.  I was adding so much gear oil that I drained the gearcase to see what came out, and there was also a lot of water getting in, but the water stayed low, and emulsified into the marine gear oil  as it should but couldn’t migrate up to the reservoir where I could see it.  When I bought replacement seals, I learned there was a change (probably because a lot of them were dislodging)  that added a plastic retainer between the two seals, taking up space so they couldn’t dislodge to a crooked, leaky position.  Note the OEM seals had this change, but Sierra did not.

Dave

[elgin2]

crosbyman wrote:

and then again   in  E.wawrzynialak “CHEAP OUTBOARDS”  if the leak  does not seems ” to bad”  one can simply  flush and refill with  new cheap GC oil….

“In most cases, the amateur was probably better off with the milky gearcase he started with” …Fleetwin

but if your  are going to become addicted to oldies  … practice makes perfect,

the shift rod o-ring is tricky but easy to do  (check utubes)  on tapping and extracting that brass plug above the oring.

I remember Frank Robb talking about the bushing above the shift shaft O-ring. His comment was on re-assembly…”Don’t pound the daylights out of it!!”  I still smile when I replace one.

[Ken Smith]

I sure miss Frank’s advice and knowledge.

www.kenadianoutboards.com

[Evan VanBeelen]

Thanks for all of the advice. Thankful I asked rather than guessing.

And Fleetwin, I appreciate the warnings. I didn’t crack open the gearcase thinking it was going to be easy, but it is something that I want to learn. I’ve got a lot of experience rebuilding engines and transmissions on four wheelers, dirt bikes, etc. so I understand the importance of the seemingly unimportant and easily overlooked steps of reassembly. I’m just new to outboards (as all are at some point), but am extremely interested in learning because I love the mechanics of what makes them tick.

[fleetwin]

Evan VanBeelen wrote:

Thanks for all of the advice. Thankful I asked rather than guessing.

And Fleetwin, I appreciate the warnings. I didn’t crack open the gearcase thinking it was going to be easy, but it is something that I want to learn. I’ve got a lot of experience rebuilding engines and transmissions on four wheelers, dirt bikes, etc. so I understand the importance of the seemingly unimportant and easily overlooked steps of reassembly. I’m just new to outboards (as all are at some point), but am extremely interested in learning because I love the mechanics of what makes them tick.

Sorry for the rant, hoping you got the answers to your questions.   Let us know how you progress and any further questions/issues you might have.  D

[Author]

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