Caulking the Keel

[_m_miles]

I am a newbie with a Beneteau 331, and am preparing to launch it for my first season. One of the required tasks is to re-caulk the keel. I have selected 3M Fast Cure 4200 and understand that I should clean the area with acetone before applying the new caulk.

My question is, should I use a metal primer on the iron keel? No one I've spoken to has mentioned this but the data sheet said it might help.

Thanks for the help!