Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

classiccat · Aug 13, 2013

I'm at the tail-end of restoring a '75 70Hp 3cyl Evinrude.

I cranked-it up for the 1st time this past weekend and a warped outer exhaust cover eventually revealed itself (2:38):

It's flat until the last 2.5"...from there it deflects as much as 0.040".

A replacement cover will be here tomorrow; the other surfaces are flat (the thin inner-plate is actually new old stock; the original was pitted & twisted like a pretzel).

My plan is to continue using a light coat of OMC gasket sealant on all 3 exhaust manifold gaskets.

.

Are there any sealant(s) that you'd recommend over the OMC-stuff for the exhaust manifold?

Also, the last adapter plate gasket that I installed was pre-coated (shiny...sticking to the bag). I ordered a new one and plan on installing it as-is (assuming that it's also pre-coated)...with no additional sealer. Good Plan?

I'm hoping that this is the last time the powerhead is pulled in my lifetime :lol:.

Thanks in Advance!

boobie · Aug 13, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

You got it all together....Keep on going and don't change your plan.

classiccat · Aug 13, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

boobie said:
You got it all together....Keep on going and don't change your plan.

Thank you for the reassurance boobie!

HighTrim · Aug 13, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Blue Fin, Ill assume the "ee-YEAH!" was a shout of triumph!?

I smiled to myself seeing how happy the start up made you. Been there many times myself. Very satisfying hearing it fire for the first time isn't it?

As Boobie stated, seems like you are very organized and have your ducks in line. I am very impressed with your testing setup! Did you actually mount gauges as well? lol

classiccat · Aug 13, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

HighTrim said:
Blue Fin, Ill assume the "ee-YEAH!" was a shout of triumph!?

I smiled to myself seeing how happy the start up made you. Been there many times myself. Very satisfying hearing it fire for the first time isn't it?

As Boobie stated, seems like you are very organized and have your ducks in line. I am very impressed with your testing setup! Did you actually mount gauges as well? lol

Thanks HighTrim!!

I was definitely amped that she popped to life so quickly...plus it was so loud that I didn't think that my victory yell would be even audible...the Admiral's reaction indicated otherwise :fish: :lol:

I spiffed-up the PowerPilot and refit it with a new ignition switch (I was getting leakage to the kill circuit), added a tach, kill switch & a head temp sender/gauge. I think it would be easier to list what I didn't fix/replace on this old 'Rude! :lol: (see resto-thread)

classiccat · Aug 21, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Update (alot-of-good ...but some bad)

The new manifold cover arrived & installed.

Before attaching the LU, I performed a few leak checks.

1st: Low-pressure compressed air (disaster check...wouldn't want to fill the crankcase with water during the next test). Put each cylinder at BDC (measured with a pencil and marked masking tape) and listen for air leaks.

2nd water hose connected to the motor's water tube (controlled with a garden nozzle)...exhaust manifold is completely buttoned-up inside-and-out.

Now for the bad news, I have a leak under the powerhead.

...suspecting that it's the base gasket despite the fact that it's a brand new gasket, surfaces are clean and I didn't find any low/high spots. The new gasket appeared precoated (sticking to plastic bag) and I installed it as-is.

The plan is to pull the powerhead again and reconnect without the lower motor cover to try and pinpoint the leak.

Bosunsmate · Aug 21, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Which gasket do you think it is?
The one directly under the powerhead or the one under the exhaust adaptor?
If its the exhaust adaptor then it shouldnt be affecting water intake, i d just high pressure high temp epoxy weld plug it.
But as my woman would say im no perfectionist

classiccat · Aug 21, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Bosunsmate said:
Which gasket do you think it is?
The one directly under the powerhead or the one under the exhaust adaptor?
If its the exhaust adaptor then it shouldnt be affecting water intake, i d just high pressure high temp epoxy weld plug it.
But as my woman would say im no perfectionist

:lol:

I suspect that it's the powerhead to adapter plate gasket. It's leaking into the area under the upper motor mounts.

Pmccraney · Aug 22, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Oh man, Chris... what a bummer! Like plugging a dam... One leak gets patched and then it shoots out another.

Its personal now - You will win!

classiccat · Aug 22, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Pmccraney said:
Oh man, Chris... what a bummer! Like plugging a dam... One leak gets patched and then it shoots out another.

Its personal now - You will win!

I appreciate your vote of confidence Patrick! It's a good thing that I love this stuff! :lol:

I'm afraid that this leak was there during the testfire 2 weeks ago...I wasn't sure if it was water spewing from the bottom of the exhaust manifold finding it's way over to the adapter plate (that's a bit of a stretch).

Both OEM base gaskets that I've installed are paper-thin. I see the V4's and V6's have upgraded to a beefy sandwich base gasket...I can't seem to find a similar upgrade for these 3cyl loopers. <- Is there one? :noidea:

Bosunsmate · Aug 22, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Yep the V4/V6s are good and thick, even a 1980s 60hp in line i did the other day had a thick gasket. That was a BRP gasket.
You could buy a gasket sheet and use a paper one to trace and cut out your own fat one

classiccat · Aug 22, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Bosunsmate said:
Yep the V4/V6s are good and thick, even a 1980s 60hp in line i did the other day had a thick gasket. That was a BRP gasket.
You could buy a gasket sheet and use a paper one to trace and cut out your own fat one

Isolated the leak & measure 0.005" recess in the adapter plate where the water enters the powerhead. Fortunately for me the block is true.

Bosunsmate · Aug 22, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Why do you think it happened there?
In NZ we generally for everything work in metric so ive just coverted it. That .005" is only an eight of a millimetre. Thats really tiny

classiccat · Aug 23, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Bosunsmate said:
Why do you think it happened there?
In NZ we generally for everything work in metric so ive just coverted it. That .005" is only an eight of a millimetre. Thats really tiny

Gasket removal would be my 1st guess..and I'm likely to blame

eep: ...for the first time, I used a fine fiber sanding disk over my trusty razor blades + acetone....Never again. Besides, there's nothing like the dizzy feeling you get after being hunched-over a container of acetone for an hour :lol: (kidding folks...acetone vapors will turn you into Gary Busey)

Yes, very small...i had to really get in there with my feelers. However these gaskets are the thinnest I've seen on this engine (from BRP as well).

I'll swing by the Evinrude dealer tomorrow am to see if he can get me something with a little more substance...otherwise, I'll have to get creative.

Bosunsmate · Aug 23, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

ha Gary Busey, thats one wild guy

classiccat · Aug 23, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

313763 -> Thin OEM Gasket
328618 -> Thick OEM Gasket
(page 166)

Bosunsmate · Aug 23, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Thats a good find.
A you going to dress it?

classiccat · Aug 24, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Bosunsmate said:
Thats a good find.
A you going to dress it?

Thanks!

Assuming that it comes precoated, I won't be dressing it; the adapter and powerhead are tough-enough to separate with just the pretreated gasket (thinking of the guy who has to disassemble it 40 years from now )

classiccat · Aug 28, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

After a few fleabay steals that included:

New Exhaust Manifold Cover
Used (Very good shape) inner baffle
Used (Excellent shape) adapter plate
Thicker version base gasket

Rebuild & Hose-test:

bonz_d · Aug 29, 2013

Re: Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

Nice video! Will have to read your resto thread tomorrow.

Gasket Sealant Recommendation(s) for Exhaust Manifold and Adapter Plate

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