My dealer installed a new aluminum drain plug sleeve in the transom of
our small fiberglass runabout ... the old one had oxidized and split.

Sadly, the new sleeve is also leaking because the transom plywood is
starting to fail and the plywood hole has enlarged a bit.

I can "buy" one more season by plugging the original hole and drilling
a new hole in solid wood elsewhere on the transom.

Should I "plug" the existing "punky" hole with glass and resin, or is a
better solution to search for a threaded through-hull fittling with
broad "shoulders" to load-up with caulk?

Yes, I know I need a new boat. grin

Thanks for your help!