The traditional way of filling partially with red lead and drifting in
wooden plugs is still the best because access to the bolts is easily
acheived when required. The plugs can be glued, cut off and faired then
drilled out whenever it is required.
Steve

"lupi" wrote in message
...
Ahoy, I'm using the last of our decent days to do the bottom of a
fiberglass keel boat. The bottom of the keel section is wood which is
bolted to a partial keel of fiberglass. (some kind of add-on from a
previous owner, I think). The bottom of the keel has empty plug holes
where the bolt heads are visible. The nut and washer arrangement is in
the bilge. I would like to fill the holes outside, at the bottom of
the keel to make it more fair. Would W. Marine marine bondo be the
thing? I'm sure the keel is tight and not about to move. Thanks as
always.