Couple of questions to ask your self and observations just before you go off thinking it's all great then some thing tragic occurs especially due to the recent high public situation with keel failures,
1) How old is the vessel?
2) Is water
still dripping/leaking (how long did it drip if now stopped?)
3) Carefully check for any small cracks around the joint line both out side and inside
4)Are there any signs inside that the bolts have moved(GRP cracks where covered over?
5) You may have to remove some floor boards or the more permanent sole boards to inspect
6) Do all the removable floor boards still come up easily?
7) Do you get un explained water in the bilge
Yes most external keels will move slightly and quite possibly have a hairline crack with as in your case rust from the cast keel but you need to evaluate the above first, The movement or lack of goes back to the flange area and system used and type of sealant
used (5200 is a good keel "Glue" ) and dont see to many failures when this is used,
The issue being you dont really know where the rust is coming from probably the keel but who knows-vessel age is prudent here! and having the keel bolts
encapsulated dosent help if the water is seeping in from the keel to hull joint,
I recently removed a Jeanneau
keel (Cast) for the same reason now the nuts on the top under the GRP where all good except 2 , but the real issue was the head
of the bolt (countersunk type located out side the hull in the keel) every one was wasted by 70 -90% and probably would have pulled through the keel easily in heavy weather
or grounding /striking a submerged object,
I can find the pictures and post if you desire to scare your self!
All that said I'm not trying to do that at all
and some other posts are quite probably correct in there assessment, BUT as I do this for a living I prefer to err on the side of caution in these possible life threatening situations - in the last keel falling episode where the owner new of possible keel issues
caused loss of life and now being charged with criminal intent. Just be prudent!!!
I offer the forgoing only as advice
with no preconception, with no legal
implications and without prejudice.
Cheers Steve (IIMS Surveyor/ Lloyd's accredited)