What kind of keel?
A few thoughts....is the keel cast iron versus lead? I had a C-25 and it was a cast iron keel.
It doesn't look like the small washers under the nuts are adequate to distribute the loads of the keel. There should be larger backing plates, not sure if the bilge is flat enough to accept a larger backing plate, but I would suggest maybe you pull the nuts and washers and look at the bolt underneath. My catalina keel bolts had severe rust on them and would probably have failed but I sold the boat versus fixing them. Definitely not a high grade of stainless used on the bolts. These bolts look pretty good in comparison but all that rust in the bilge would make me want to look. Maybe the owner would let you remove one at least for inspection. Stress is equal to force divided by area, so the larger the backing plate for the nut the more area you have to spread the load and reduce the stress. As the keel is putting a large static and bending load on the boat having all the stress concentrated in the small washers is a poor design. My C-25 was the same, I'm sure the Catalina designers did their homework and can show a nice safety factor but the added cost of a couple of stamped stainless plates with a hole in them to spread the load would be pretty insignificant to the cost of the boat. I would suggest you make some backing plates or buy some, put some saran wrap over them and coat the studs with some kind of release agent. Then mix some epoxy with some fibers or maybe some squares of cloth wetted out to slip over the studs, then put the backing plate down over the stud and tighten the nuts finger tight or so. Once cured this should give a nice flat surface for the backing plate to spread loads into the keel stub. Remove the hardware, remove the saran wrap then torque it all up. Maybe add a little 3M 4000 sealant to keep bilge water away from the studs under the backing plate before torquing.
