Man, I wish the previous owners of some of my last boats had the sense to ask this question...
surfaces are usually a composite made up of fiberglass
laminate on the top + bottom and a "core" in the middle, usually wood, sometimes foam. Like a sandwich where the bread is fiberglass and the meat is "core".
When you drill a hole in a composite, you need to make sure you protect that "core" from future water
intrusion. Too commonly people assume the thing they are sticking in that hole will be "bedded" with some junk and all will be well and watertight. A few years later the bedding fails, water
starts weeping in, and slowly but surely the "Core" is rotting and getting soggy and ruining the structure.
When I drill holes in such a structure, I drill the hole, then I gouge out the "core" surrounding the hole, then fill the whole thing with epoxy
, and then re-drill my hole when it cures. This way the core
material is safe + dry on the other side of that epoxy
even if the stupid doodad I stuck in the hole is no longer watertight. Better to have just a leak to repair than a leak and a rotten deck
And probably best not to put this somewhere where water pools.