Thanks, Gary, good input.

I was going to tap a small hole (or two, the second one for air intake) and just use a machine screw with a rubber washer but a tire valve sounds like it might be even better. My only concern with pressurizing the mast is the possibility of blowing out existing seals (ie, siliconed areas). Did you have any problems with that?

One advantage of a valve (probably theoretical at best...) is that if you were capsized and took on enough water at your comptip to make righting difficult is that if you had a small handheld pump on board you might be able to push the accumulated water in the mast top temporarily back out the point from which it leaked into the mast in order to right the boat (although you wouldn't be able to get it all out since it will run "downhill" from the point of leaking). This might be worthwile trying if one was cruising, as you do, where you might be quite a ways from help.

Why did you place the valve on the front of the mast instead of on the back? At least on my H17, below the level of the bolt rope prefeeder the back of the mast is cut away exposing the flat wall at the front of the mast bolt rope channel. This seems like it would make a very nice place to place a hole/valve.

Finally and very importantly, do you know how high from the bottom of the mast (ie, point where the mast extrusion meets the mast base casting) to drill so that the hole ends up just above the level of the bottom plug so all of the water can be drained?

Thanks for the help!

Jerry