Gasket Sealer on Cylinder Head Cover

[Bob Wight]

I’m putting the powerhead back together on my ’82 Evinrude 25hp.   Should the gasket for the cylinder head cover get gasket sealer?  In attached pic, the old gasket on the left definitely had NO sealer on it.  When I took it apart, the original gasket came off very easily with no sealer residue on the gasket, the head or the cover.  The couple areas on the old gasket that appear as torn/damaged was caused by my lifting the gasket off with a putty knife, not from a gasket blowout or failure.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1957 Evinrude 3022
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20
1982 Evinrude 25hp

“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."

[Don]

Yes, definitely use some of the light OMC/Merc/Yamaha liquid gasket sealer on that water cover gasket.  Do not use silicone or any goop like that.   During factory assembly, oftentimes no sealer is used because the surfaces are flat with no imperfections, so the plain gasket seals up just fine dry like that.  Be sure to apply gasket sealer to the bolt threads as well, so they don’t rust in place.

Be sure to clean out that thermostat cavity completely.   The inner bore needs to be cleaned out so the thermostat slides up and down without binding when the pressure relief activates.  The area underneath where the thermstat/rubber gasket sits must be cleaned up carefully also to be sure it seals well when the thermostat is sitting flat on the head (pressure relief not activated).   If this is overlooked, water will sneak around the base flange of the thermostat/gasket and the engine will not heat up sufficiently at idle.  These engines are very cold blooded, and need to develop some heat to run OK at lower RPMs.

[Bob Wight]

Thanks Don.   I typically use Permatex Aviation gasket sealer when a sealer is needed so I’ll use that.   I always use that same sealer on the head bolts.

You are correct on the thermostat housing – I’ve made sure the head cover pocket and inner bore are absolutely clean.

 

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1957 Evinrude 3022
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20
1982 Evinrude 25hp

“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."

[Author]

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