Be really careful how you do this...
The deck of the boat is end grain balsa cored for stiffness; great but if its exposed to moisture, the water spreads through the balsa, softens, delaminates, and rots. This is a major expense to repair.Silicone and other non-adhesive sealants will wick water by capillary action under hardware and into the deck. This is very common and one of the chief reasons to hire a pro surveyor for a used boat. The right way to mount new hardware:1. Drill a small pilot hole in the mounting position.2. drill out an oversize hole from the underside of the deck, maybe 1/2" in diameter larger than the hole needed, up to but NOT through the upper skin on the deck. 3. Tape over the larger hole on the bottom and fill the Hole with solid epoxy.4. After it hardens, drill the actual hole you need to mount the new hardware. Since the hole now goes through solid epoxy, moisture won't get in your balsa core.5. Seal the hardware with an adhesive. 3m 5200 is the best, but it is quite nasty to remove. If you do need to remove 5200, try this: http://www.antibond2015.com