Head gaskets.....sealer or no sealer????

[JOFO17]

I'm replacing the head gaskets on my '81 200 hp Johnson this weekend. I have brand new factory head gaskets. The Johnson tech manual says to use a Johnson head hasket sealer, but I've read several posts that say to use nothing at all. I've read just as many saying to use a sealer. I looked and my head gaskets do not say anything either way about sealer. Years ago we used to use the aviation sealer on our outboards, but I realize the materials used to make the head gaskets are different then back then. I'm not sure what is best.

 

[Grub54891]

I never use sealer on any headgasket. Make shure the surfaces are flat,tourque to specs,done. However,if the factory manual says use it,maby I would. What kind of sealer is it??

 

[Tim Frank]

If it is an OEM Johnson manual, follow their instructions.

 

[HighTrim]

If the gasket has a shiny coating, that is the sealer. Some of the older gaskets did not have it when the manuals were written. However, most of the gaskets with the shiny coating also state on them NO SEALER REQUIRED.

 

[emdsapmgr]

My 78 V6 manual says to apply gasket sealer to the head gaskets-unless they are marked "no sealer required." Your 81 manual probably has similar wording. Most factory replacement head gaskets sold today do have that marking, so no sealant is required. Not sure what markings (if any) are on aftermarket head gaskets.

 

[Bosunsmate]

Just wondering is it better to drop the lu before installing the headgasket and giving its first run to heat and cure the sealant?
As if you keep the lu on the water pressure will affect the sealant wont it?