How to close discontinued thru hulls.

hastingsml · #1 04-26-2006

I am considering a sail boat that no longer has an inboard and will be inspecting it this week. Without the inboard there are three holes in the hull that will no longer be used; prop shaft hole, cooling water intake, and cooling water discharge.

When I looked at the boat the first time I didn't pay much attention to these things but the intake does have a gate valve on the thru hull.

How should these openings be handled?

sailingdog · #2 04-26-2006

They should be glassed over, if they're not going to be used. Anything less is just asking for trouble.

Faster · #3 04-27-2006

Agreed. Properly glassed in and faired inside and out, no more worries after that. Through-hulls left plugged or capped are just accidents waiting to happen.

Jeff_H · #4 04-27-2006

More to the point, the holes should be ground out from both the interior and outside side of the hull with a 1:12 taper (or until you hit solid glass- water often seeps into the laminate around through hulls). The holes should be filled with multiple layups of epoxy and fiberglass cloth. I like to lay up to a couple extra layers on the interior of the boat that extend an inch or so beyond the edge of the repair.

Jeff

hastingsml · #5 04-27-2006

is it possible to just remove the thru hull and fill the hole with epoxy?

If I want to keep the hole available for the diesel prop shaft, just in case, how should I make this opening safe?

Jeff_H · #6 04-27-2006

The holes in question are too large to simply be filled with thickened epoxy which is what I assume that you are suggesting. You need to close these holes properly. Should you decide to reuse these holes in the future, the reality is that you will still need to have them closed properly and then drill proper diameter holes for the new shaft log and through-hulls. Properly closing the holes now mean that you will save that step in the future.

Jeff

sailingdog · #7 04-27-2006

No, I would still recommend glassing in the holes and then re-gelcoating. The problem with a plug is that you really do risk sinking the boat rather quickly.

The prop shaft is probably two inches in diameter, at near the very bottom of the main hull. The amount of water that would come in through that hole, if the "plug" ever fell out, would probably be enough to overwhelm what bilge pumps you have in a matter of minutes. Then your boat would quickly fill up and sink.