I have seen this before
I have a Columbia 34 MII that I bought in December 98 the previous response to get a good marine surveyor to look at the boat is a good idea.I have had the same issue since I bought the boat and what I did was add six bolts to the keel sealed with epoxy so far so good!!! The only thing I would have done different was paint the new bolts sooner as they have discolored my bilge. Not a super big deal. I you haul the boat and grind out a quarter inch gap let it dry out for a while and then fill and fair it and add a layer of glass I bet it would last quite some time. However make sure you have a GOOD surveyor look at it. I hope this helpsCaptain Pern