Check the torque on your keel bolts
Earlier Catalinas, like the 27 had a plywood floor that the keel bolts went through. This plywood has eventually taken on water and many C-27s have the smile. The cure is to replace the plywood floor with fiberglass because the more you torque up the bolts the more the floor collapses. In your boat this shouldn't be a problem, but maybe you should check the torque on your keel bolts<nuts>. Ask Catalina what they should be and use a torque wrench to snug them up. Next time the boat is on the hard, (weight off the keel bolts) do it again. Just my opinion, but if you are taking water, or getting seepage (salt crystals?) around the keel bolts, then this gets more serious and you may have to chamfer a v at the keel hull join and caulk it, as well as tighten the bolts.