If I am just going out sailing for an hour or so, I just shut down the motor. If I am out longer and/or overnighting, I shut off at the tank, letting the engine suck out the remaining propane (at idle takes about 1 minute). That way there is nothing left in the lines to leak and if I need to remove the tank, no propane blowout. If I am going to be away longer, I disconnect the tank and store elsewhere (usually home). I feel more comfortable limiting the times that I have pressurized propane in the rubber supply line. I am not an expert, but I think on boats with larger propane tanks and integral appliances, the boat code discourages any fittings (tees, valves, even shut-offs) after the tank. I suppose the thought is the more fittings you have, the more places to leak! So I bought an adapter with an integral shut off, and I make sure everything is tight before I start the engine, when I shut it off, and before I leave/sleep on the boat.