On land, a gas leak drifts away. On a boat it sinks. Propane is heavier than air, so it settles into the bilge, the locker, the cabin floor, and sits there. One spark from a switch, a fridge compressor or the starter is enough. Boat gas safety is not paranoia; it is a short routine you repeat every trip.
The cylinder stays vertical, always. Lay it on its side and liquid can reach the regulator and damage the valve seat. Keep it in a ventilated spot outside the cabin, away from hatches and openings, and strap it down so it cannot slide with the swell. Check the hose every trip: if it is stiff, cracked, or shows heat marks, replace it. Clamps must be tight and correctly seated. If the cylinder body is rusted or deeply gouged, retire it instead of arguing with it.
Mix water and dish soap in a spray bottle, then coat the valve, hose and every joint. Bubbles mean a leak: shut the valve, move the cylinder to open air, and ventilate before anything else. Never use a lighter or a match to hunt for a leak. Smell is a warning, not a test: the odorant can fade in your nose after a few minutes, and some people stop noticing it. Soapy water is the verdict.
Open the cabin and hatches and let air move for at least a minute before lighting. If you smell gas, do not light anything and do not touch an electrical switch. Shut the cylinder valve, carry the cylinder to open deck, and let the space air out. After cooking, close the valve at the cylinder itself, not just the burner knob. Turning the gas off at the valve before you move the boat or go to sleep is the habit that matters most.
Never cook while refuelling, and never light anything near a fuel filler. Secure the stove and the pot so nothing slides when the boat rolls. In choppy weather, postpone cooking or eat something cold; spilled oil or a tipped pot over a lit burner is a serious problem. Before heading out, check sea state in B7R and decide whether cooking on board is worth it.
Carbon monoxide is the quiet one. Stoves and engines produce an odorless, invisible gas, and an enclosed cabin traps it. Never sleep with a burner lit or with the engine running and the cabin closed. Fit a CO alarm if you can, keep a fire extinguisher within reach of the cooking area, and know how to use it before you need it. Agree on a plan: who shuts the gas, who opens the hatches, where everyone gathers.
Build the routine once, then let it run itself. Download B7R from Google Play to check sea state, tides and seasons before you leave the dock.