OMC Lower Unit Sealant and Questions

[raglover]

A question that has been asked and answered many times but I have lost my notes.

OMC split case lower units with spaghetti seal use 3M scotch weld 847, correct?
Crank case halves use something different, I seem to remember Loctite 518 as a modern listing, correct?

I have used the 847 in the past on lower units, the tube is old and I am going to replace it.

Recently I have had two big twin lower units leak oil from the prop seal on seemingly good shafts with new seals (I did total reseals)–has anyone seen a problem with the BRP, SIerra, or other seals on the prop shafts? I am pretty sure I used the BRP kits May be coincidence but two units have leaked after very little use from this seal and now I am going back in and want to make sure I have my ducks in a row. Also have a third that needs to be done and only want to do it once.

Thanks,

Allen

[legendre]

I have no experience with the sealant materials you mention, but I can offer some info on the leaking seals.

First you need to nail-down (if possible) if the new seal is leaking around the OD (where the seal meets the case) or the ID (where the shaft penetrates the seal). If the former, you need to look at things like seal-to-case fit, and so on – sometimes driving the seal into the case will shave off critical outer material, causing leaks at that joint. If the latter, the most common way seals are damaged is by burrs or sharp splines on the shaft that is being sealed, as the shaft passes through the seal lips, damaging them.

Did you pilot the seal onto the shaft (even with a turn of tape, if you didn’t have a seal pilot tool)? It’s so very easy to put multiple little cuts into those seal lips if you don’t protect the ID of the seal from the OD of the shaft. Your eye will miss them, but unfortunately the oil will not.

[chris-p]

I would guess that she is leaking where the spaghetti seal buts to the prop shaft seal housing.

There should be 1/16 overhang. No more, no less. Any more, and the spaghetti seal will buckle, creating leak spots. Any less, and of course it will leak there. Perhaps your spaghetti seals were cut too short? When you drop them in, push them to the outer edge of the groove to ensure they wont shrink.

[frankr]

And make sure the spaghetti is trimmed square on the end. Tapered doesn’t get it. And yes 847 is the stuff.

[outboardnut]

I also had problems but I took Franks suggestion and 847 is the way to go

[chris-p]

I use the 847 in my gearcases, and in my crank halves with the spaghetti seal. Great product for both. Never an issue. Not cheap, but who wants to open these items up twice!

[beerman57]

For the block, OMC Gel-seal or NAPA has it in a tube you will never use it all. Anerobic sealer (sic?), strawberry red and gooey/sticky as can be. I just got some from NAPA because I was scared to use my old tube of OMC stuff, but I think it would have been OK?

[raglover]

Thank you for the replies. I did use a seal install tool but not sure if it is any good for the piloting part of sliding the gear head over the shaft, I always just lube the prop or drive shaft up really good–should I do something else?

I will need to go back and really look at where I am leaking. The spaghetti seal would actually be a welcome surprise. I will heed the advice of 1/16 overhang as I do not always make sure I have that, always flush at least and square for sure but not with the minor overhang.

Thanks for the confirmation on the 847. I use it on the lower units and have used it on OMC crank cases with the spaghetti seal, but I have a Merc on the bench that does not have the seal and was thinking the anerobic stuff was the way to go. I will check Napa, the Loctite 518 is red too, thinking it might be the same stuff.

Will reseal this weekend.

Thanks for the help!

Allen

[raglover]

I finally got out to take a look a my two leaking motors.

First 1959 evinrude lark super quiet model 35 hp
Found the leak and oh no there is a lot of prop shaft play. So much that I can move the shaft side to side and the oil comes gushing out around the seal

Second a 1956 evinrude 30 with a later model lower unit
that has the same prop shaft as later models without the screw on prop nut

It leaks at the back corner between the halves according to bubbles on pressure test. However it has some prop shaft play too, not quite as much but some

So the question is how much is too much on shaft play and what is the main culprit before I go tear into one? The 35 leaked so bad it lost oil and I did not know so I expect carnage although it did not fail in operation.

History
I resealed both these units and did some parts swapping from the donor stack to replace worn bearings and one very worn prop shaft seal area on the 59

but no parts swapping on the later lower unit on the 30, which was pristine when I opened but it had been sloppily resealed at some point by the amount of 847.

In no case did I not swap the whole gear set if I ever swapped gears (cannot remember)

Sampled the other big twin lowers in the shop.

Another 59 I resealed years ago, no prop shaft play
1956 30 I have never touched, no play
1960 gale 25, no play
1957 johnson 35 that had prop shaft and gear set from a later unit swapped in after dog failure—-very minor play

Worn casings? To my knowledge upper and lower halves match and I lapped flat at reseal on glass plate with 400 grit.

Troubled and confused.

[frankr]

That is a ball bearing in there, so there should be virtually zero play in the bearing. But I suppose it is possible for the shaft to be slopping around in the bearing, or the bearing in the housing. Good thinking on the possible mismatch of the housings. I’m thinking about the front bearing, a tapered roller bearing. But it would have to be pretty bad to make it sloppy at the aft end. I don’t know, keep us informed on what you find.

[Author]

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