Sealant
 

While the engines were out for maintenance I am replacing the indicator cables to the outdrives. What is the sealant used under the covers where the cables go thru the stern? Its black if that helps. Thanks

black 4200

Its probably just marine grade black silicone sealant.

Indicator cables? The wires going thru transom assy? They also are in a rubber grommet. I would look into getting a new one of those. It is barely above the waterline. Also, you need wire that can handle that environment. It looks like a cord off a lamp, but it is not...

He's talking about mechanical trim indicator cables with the clam shell cover.

Then they are well above waterline and whichever permanent sillycone closest matches the hull color.