What's the general consensus on the transom assembly seal when it comes to needing sealant? I've seen comments from dry or needing a coat of grease to needing 4200. I know 4200 wouldn't hurt, but is it really necessary? The transom is in excellent condition and flat. The assembly is new Mercruiser.

Buddy had one done a couple years ago. Factory put original in dry and it was still good with no signs of leaking after 15 years. New assembly/gasket was put back on same way. Like your boat his transom was nice and flat.

The only thing that has me wondering is the material the gaskets are made of. The one I removed seems to be rubber where the new one is foam. I coated it with grease, but now I'm second guessing before I put the motor back in whether I should use 4200 sealant.

Put it on dry

Grease is not good and can cause the seal to break down depending on what the gasket is made of.

I already applied a little grease and installed the assembly. The gasket is foam like a cars trunk gasket.

I installed dry in 2018 and no leaks since.

Remove, clean with dawn dish soap

Agree it appears to be like a truck gasket, but I also installed new and dry some years back

Never put a thing on one. Grease/gas/oil breaks down rubber.

Agreed grease is a bad choice. What is the benefit?

I did mine a few years ago, and added a very thin film of silicone to the edges of the assembly (not on the seal itself).

What about marine lithium grease? It's not the same as regular petroleum wheel bearing grease. Just trying to figure out if it's really necessary to pull it back off. Thanks.

Edit: I think I answered my own question. It's still petroleum based so I guess I'm pulling it off. Thanks for all the responses guys.
Last thing... fwiw, the new seals aren't really rubber, but a foam like seal it seems like.