Home-made gasket for 2-stroke motor

[Al Deveron]

I am rebuilding a 1988 Evinrude Junior 2hp outboard motor. I have cut myself a paper gasket to go between the leg and the upper casing. The gasket needs to be gas-tight for hot exhaust gasses. There are also a couple of small holes in the gasket for cooling water channels.

The gasket paper I used is 0.6mm thick. My question is: should I smear anything on the gasket before reasseembly? I have some lithium grease. I also have some blue silicone gasket compound, and some silicone grease. Which of these is most suitable, if any?

Thank you.

Al Deveron

[Guy King]

The message from Al Deveron contains these words:

Personally for things like that I've always preferred Hermetite Red. It's non-setting so copes with slight thermal movement - and though not usually suitable for exhaust duty I don't think it'll get hot enough in an outboard leg to be a problem.

[Al Deveron]

Thanks. It will be nice if I can use something that will enable the gasket to be reused next time the joint is separated. Do you think Hermatite Red will allow that? If it's the same red Hermatite that I used to use in the late 1960s on my motorcycle, I seem to recall it did used to set pretty hard after a while. Perhaps they changed the formula at some point.

Al D

[Doki]

I've heard of bathroom silicone being used quite successfully on car exhausts.

[Guy King]

The message from Al Deveron contains these words:

Generally. It's rather good at allowing things to seperate. In fact, it's weakness is one of its strengths. It's leakproof but not an adhesive. Just what you want in a gasket.

[Dave Plowman (News)]

I've never seen an exhaust gasket made of paper. They're usually some form of metallised material - or copper, etc.

[Dave Plowman (News)]

There is a silicone sealer for exhausts, but I'd assumed it was to a different spec to the domestic stuff - although of course not all joints on an exhaust get super hot.

[Guy King]

The message from "Dave Plowman (News)" contains these words:

It's quite common in outboard legs - after all the exhaust is quite cool by the time it gets down there.

[AJH]

Envirograf silicone fireproof sealant is rated to a high temperature but it's really for brickwork to steel. I have an unopened tube that's past its sell by date if the op is near NW Surrey.

If it's anything like a Johnston outboard I reckon a normal engine plastic gasket would work as the water gets mixed with the exhaust and thus the temperature is low.

AJH

[The Natural Philosopher]

The correct thing is a proper gasket compound.

And proper gasket material..both used to be available in DIY car repair places.. the red stuff used for fixing gas leaks is probably close enough though.

I am unsure if silicone gasket stuff will take the heat.

[The Natural Philosopher]

Its the same, and its pretty good., I couldn't remember its name. Used it a lot rebuilding car engines in te 70's.

It DOES come apart eventually. If it needs to. Better than a copper gasket corroded to a cast iron block anyway..

[Dave Plowman (News)]

Ah - ok. Boats are somewhat foreign to me. ;-)

For the OP, my favourite jointing compound is Blue Hylomar. Easy to remove when required with cellulose thinners.

[kevin foote]

Regular paper inst really suitable for head gaskets. Can you not source a proper OEM part? Blue silicon sealant you have is prob best, but if you hadthe correct part nothing or a very very thin smear of hermitate red gasket goo.

Kev

[Guy King]

The message from "kevin foote" contains these words:

True, but this isn't a head gasket. It's half way down the leg.

[Al Deveron]

I thought it was the "golden" Hermatite that was formulated to never go hard. At least that was the case when I was rebuilding British bike engines in the 1970s. To my amazement, the stuff is still available, and I bought some today....

Al D

[Al Deveron]

Yeah, the temperature won't get terribly hot, since the joint is in alloy which is connected directly to more alloy that is getting dragged through cold sea water. Spares are rather hard to come by. Hence my cutting a paper gasket. I ended up using Golden Hermatite, and will keep my noodles crossed.. I figger that since Golden Hermatite is still on the market after about 40 years, it must be OK.

In my day, there was Red Hermatite, Green Hermatite and Golden Hematite. Red Hermatite was the sh*t we all avoided like the plague. Golden Hermatite was useful. We never figgered out what Green Hermatite was for. Or perhaps we did, but kept forgetting!

Al D

[Al Deveron]

Thanks for confirming that. The old gasket certainly looked like paper...

Al D

[Dave]

The word is figured, I think?

Dave

[Al Deveron]

Yes, I purchased some "proper" gasket paper for the job.

I am sure it would. However, I have reservations about silicone, because bits of it can end up causing blockages in oilways, etc. That's why I ended up using Golden Hermatite. To my amazement, it is still available nearly 40 years after the last time I used it.

Al D

Al D

[Al Deveron]

Correct. Or, at least, 1/8 the way down the leg. ;-) It's not gonna get as hot as a head gasket, that's for sure.

Al D