I work on keel bolts and about two years ago I worked on a clipper 36.
The boat was in bristol shape except the keel bolts. The nuts inside
the bilge were very rusty. The rest of the bilge was clean. We undid
the nuts with several snapping off. The bottom of the keel had cement
in the holes were the keel bolt heads are. We chipped off the cement
and drove some of the bolts out. The punch we used went along side
some of the bolts and jamed. We pulled out the punch and used a whole
jack, a hole jack is jack with a hole all the way through it.Then we
drilled and taped a 1/4 20 hole in the head of the bolts. We pulled
out the bolt head first out the bottom of the keel. What I saw was
like two ice cycles point to point. That is how the rust works on keel
bolts usually at the keel hull joint. The bolts were all different
lengths. I forget the lengths but the longest one was about 14". I
made new ones out of stainless 316 and coated them with Dophinit, I AM
NOT SURE HOW YOU SPELL IT, and then shoved them back up in the hole. I
coated the bolts realy heavy with the dophinite. I took some sealing
yarn and made a little gromet and coated that in dophinite. I then put
on a waher and nut on top and it worked. The old bolts were made out
of steel. They used white lead between the keel and the bolts. The
main thing is you have to have the keel about 18 of the ground so you
can pull out the bolts and more important is put the new bolts back
in. I forget what we used to cap over the bolt heads, I think we used
cement grout.
I do this for a living so if you want me to tare your baby appart give
me an email