You usually don’t think of a hole in your hull as being a good thing, but sometimes a properly organized one can save you a lot of trouble. Back when I owned Crazy Horse, my Alberg 35 yawl, a boat with a full keel and very deep bilges, I wished I had a bilge drain like the one pictured above every time I hauled the boat. There was always a fairly large pool of water at the bottom of the bilge that pumps couldn’t pick up and that I could never reach to bail out by hand, and I would have loved being able to simply drain it out when the boat was blocked up on the hard.
If your boat has a keel-stepped mast with internal halyards, a bilge drain, whether the bilge is deep or shallow, is practically a necessity. Store such a boat on the hard with its mast up, and all the rain entering the mast through the halyard exits gets routed right to the bilge. If you don’t get it out somehow, it will freeze up and possibly cause damage if you are in colder climes, or it may simply flood the boat wherever you are. Your bilge pump can save the day, IF there is power to run it, but the more foolproof solution is to simply leave a bilge drain open so the rain can run out on its own.
Very few, if any, production fiberglass boats come with bilge drains built in, but they’re not hard to retrofit. A nice bronze drain with a screw-in plug, like the one in the photo up top, should present no maintenance problems. Instead of installing a dedicated drain, you might instead just pull out your speed log sensor every fall and leave its through-hull open. In either case, however, the drain should be as close to possible to the lowest point in the bilge. If the boat has flat shallow bilges with a sump, the sump is where the drain needs to be.
Maybe you use an existing hole
My current boat, Lunacy, has a deep sump and a keel-stepped mast, but also came fully equipped with a very effective bilge drain, located right at the bottom of the sump. Only problem is the drain is simply a short pipe (the hull is aluminum) stopped up with a wood bung.
Lunacy‘s bilge drain, with wood plug inserted, as seen from inside the sump
Every professional who has seen this arrangement is horrified by it and tells me I must get a proper metal plug with threads. But so far the wood plug has worked perfectly.