The rules are fairly simple
If you mount the tank outside in the open it must not be above any openings into the boat including vents and windows.
All systems Must have a regulator
, a shut off valve that can be remotely operated at the appliance (stove)
A gauge must be installed before the regulator
. (to test for pressure leaks)
The supply line must have no breaks, meaning a single
line run the whole length, no splices or other connections.
lockers must vent overboard
, be air tight and top opening.
All common sense really and USCG requirements so its the law
See my article (as published in Cruising World) on propane systems here: Project Boat Zen - Maintaining your Propane system
Any questions let me know