Had to remove my 1989 70 hp Mercury from the aluminum boat in order to change the tilt / trim motor. The factory used an adhesive marine caulk around the mounts for the outboard, I guess for looks and vibration. What is the best marine adhesive caulk to go back with?
Use a polyurethane based marine caulking on both ends of the bolts. It keeps the moisture from rotting the transom core.
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Richard
Gluing geek since 2007
Opinions and intepretations expressed are solely my own and do not express the views or opinions of my employer
4200 is the stuff everyone recommends, I have always used Sikaflex 291i? but personally hate the stuff and have never found a way to reseal it after use and so end up a one shot item which I end up stabbing holes in to get to the uncured gloop. I have also found it had little flex to it and falls out of any fittings with any movement after time.
As per the above: Sikaflex 291 or 3m 4200 or 5200. The main reason is to stop water ingress into the transom rather than for vibration reduction. You can buy mini tubes as well as the big ones that go in a caulking gun. One small tube would probably be enough for four bolts. If you buy a big one store it in the freezer after use - next time you need it just defrost for half an hour in warm water - you can do that as many times as you need. If you don't the nozzle end will go off and you wont be able to use it.
