Cored deck or Solid Laminate??
What ever yu do, after you have drilled through the deck, check under the gel coat /fiberglas to see if your deck is cored material (either end grained balsa, marine plywood or foam) or solid laminate. If cored material, route out the coring, an area about 1/4-1/2 inch larger that the hole with a bent nail. Plug the hole frm underneath and fill the hole with epoxy. After the epoxy dries drill out the hole again. Not only does this provide more strength at the hole but it keeps water from soaking into the cored area and delaminating, becoming soft and eventually dripping inside the cabin. The above procedure is nicely explained in the West Systems catelog which you can get for free by either writing to them (address in most sailing magazines) or visiting their web site and requesting a copy. Go to www.sailingindex.com, click on commercial, and explore from there. You'll eventually find West System epoxysHave funMark Whitson