Sealing screw holes that don't penetrate deck-necessary?

[SpaceRnglr]

I am refurbishing my first sailboat that unfortunately hadn't seen any maintenance of any kind for 3+ years. I am rebedding most the hatches deck hardware and think I may have to replace some wet core--I don't want to do either again in the future. I know for through bolts you use an allen key in a drill to break out the core, fill with epoxy, and then drill a hole for the bolt. I am using butyl tape for all those sorts of applications and the hatches with good effect so far.

What about screws that don't penetrate the deck. I have several that hold on things like the dorade vent. I know the screw holes won't leak into the interior but I want to keep my core dry. It seems to me when spinning the screw to tighten the threads will shear off any sealant. Am I being paranoid or is sealing screws a necessary thing to do? If so, how do you ensure a good seal? I suppose the same question goes for the screws that hold down the hatch, but there is so much butyl around those screws I am not as worried...

Thanks in advance.

Mike

[MarkSF]

For screws I drill out and fill with epoxy, like you would for a through bolt, then install the screw with butyl tape. Butyl tape appears to tolerate being used on a screw.

[roverhi]

Use a 199 Dremel bit instead of allen wrenches. Works way better and won't twist the tool out of your hand.

[denverd0n]

Butyl tape works fine with screws.

[OS2Dude]

It doesn't matter if the screw penetrates the interior layer, it has penetrated the exterior layer and that is where the water gets into the core from.

If the core is still good, I stick a small string of butyl in the hole and a small amount around the threads of the screw. So far that seems to work for me. A small circle of butyl around each hole under the base plate as well as a small ribbon around the perimeter helps to keep the water from even getting to the holes in the first place.