It was a 15 year old solenoid on my new to me boat, in the sealed and vented locker as you mention. I could not get the flame to go out on the range with the unit not powered on. I thought maybe I had a short but could not find anything. I replaced the old solenoid and had to bring the regulator up to the shop to put it in a vise--it was that hard to get off--it was corroded internally. Ron C said at the time that condensation does it to his solenoid a few times. I think cruisers should carry a spare, because as you mention when they fail most often its in the closed position and if the set up is like mine, with reducing fittings there is no way to bypass the solenoid and use the range. BTY I have a tube of the propane certified goop needed for the fittings that I had to buy--good for at least my lifetime and more--ya need some?