Filling imperfections/ blisters on keel?

[Brandon Pellow]

I have sanded my keel back to bare metal and there are some spots where rust has taken hold. I have ground them back as much as possible but there are some holes that look similiar to bore holes from a insect.  I have heard that "Bondo" or similiar autobody filler is adequate to use to fair the keel before priming and painting. Is this correct? Any suggestions are greatly appreciated.Brandon

 

[Dick of Sylvan]

Marine filler

Not sure about Bondo. I'd stick with a marine producteven though they are rather "pricy". I used Interlux's "InterProtect Watertite" successfully on holes similar to those you describe in my keel a few years ago. West Marine sells it, and they also have some 3M vinylester fillers that look promising.

 

[Robert Moretti]

Don't use Bondo for this!

I've done this kind of work on my keel. I learned that any filler product that is polyester resin based is a poor choice. Reasons: polyester is less water resistant than epoxy or vinylester; and polyester repairs made underwater do not hold up as well. On my keel, the polyester repairs (Bondo) peeled off after one or two seasons. The areas that I repaired with Marinetex (epoxy-based) have not peeled off.By the way, as you are probably learning, you can't grind all the rust out without destrying the keel. Use some naval jelly to take off the surface rust. Then use an epoxy or vinylester filler. Then put some kind of barrier coat over the keel to keep water from getting to the metal. I used several coats of VC-tar because it is easy to work with.