For resealing anything the goes on/through the floor of the boat, do NOT used silicone sealant. WHEN you spill fuel or oil on the floor of the boat, it will eat away the silicone and can cause leaks.
I recommend you to use a product from PERMATEX called "Form-A-Gasket" (No. 2). This is a slow drying, non-hardening sealant designed for sealing cut gaskets and stamped parts. Allows for easy disassembly (if required). Temperature range -65*F to 400*F; resists water, gasoline, oil, kerosine, glycol, grease, propane & butane. Use where sealing is more important than adhesion.
Part# 80015 - 1.5oz. tube
Part# 80016 - 3.0oz. tube (this is the one you'll find on the shelf)
Part# 80011 - 11 oz. tube
You should be able to find this product at you local auto parts supplier.