Well that's a little discouraging to hear. I ended up going to the ramp (with only the rear floor out) and found several leaks in my transom from all the holes drilled from the fancy 80's tech that was still installed from when I bought it. I tried using marine epoxy + rivets to seal the holes...
I have a 18' 1988 bayrunner that has a similar leaking problem. It seems the previous owner tried welding the keel guard along the sides but there were a few gaps where water is still coming in. I have been thinking that the keel was likely cracked under the guard and have been saving money for...