If you are anal and want to do it right, like me, and holes will be in cored areas of the deck
, do this:
Get a Dremel 199 bit for you Dremel tool and rout out the core
around each fastener. If you are drilling new holes, just drill down to the inner skin, not all the way through. Fill the holes with epoxy
resin thickened with West Systems 403 structural filler. Redrill the holes and put a slight bevel on the topside with a counter sink bit. Caulk with caulk of your choice: LifeCaulk, Butyl, 4200/5200, etc. Use Fender
Washers as backing or make backing plates
. In no case use sillycone. Remember, "Sillycone belongs in boobs not boats."
You will probably be fine if you just hit the holes with a countersink and caulk with a good quality caulk. Don't crank down on fasteners in cored areas, you'll just be crushing the core
. I hold socket ratchet handle by the head
and just use wrist strength to torque fasteners in core.