I have a similar problem but with a 30 footer. In my case and likeley in yours the bolts will be stainless steel but the nuts are carbon steel and so rust rather badly. I my case I am going to try to get all 8 nuts of and clean up the threads. then install new SS nuts with a good thread lubricant and torque them. Hoping that will seal up the small leak into the bilge.
If not I will have to drop the keel and recaulk it.