Thanks Mike; that's great! I like this one:
Mini Immersion Proof Breather TA250-1


I could drill an oversized hole and glue it into the transom with epoxy. As long as there is a slight film of wax or oil on its threads, it will also be extractable.

Now, .... is there anybody here who can add one of these valves to their order and let me get it from you? I doubt if my local retailer will have one on their shelves.

For now, I'll use a 1/32" hole and if necessary I will cover it with tape once the hull has chilled. This will be the pilot hole for the new immersion proof gas pressure equalization valve.

GARY