Mount your propane tank outside the hull, so if there is a leak it goes into the Ocean. Mine is mounted on a platform under the wind vane at the stern, and has been in this location through many Ocean passages without corroding - it is aluminum.

We have only one tank and when it runs out we go to restaurants until it has been refilled. This way we don’t have to find a safe place for a backup tank. Tanks in sealed lockers have caused many boats to explode, because the owner forgets to tighten the connection properly and there are always small gaps in the through bulkhead holes. Tanks in the cockpit are a no-no as any small leak will accumulate gas in the cockpit unless the boat is underway. At anchor, the gas may leak into the boat while you are away. Mount a pressure gauge at the tank and turn the gas off at the tank immediately you have finished with it. Check the pressure an hour later or when you return to the boat. I don’t use an electric solenoid valve to open the flow of gas from the stove position, because I always walk to the back of the boat to turn on the gas anyway.