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Fire on board: the first thirty seconds
Fire is the loss that gives you the fewest minutes. On a plastic boat, with diesel, gas and electricity in a small space, the first thirty seconds decide the whole vessel.
Where it starts
Nearly always in three places: in the galley at the gas or the cooker, in the engine space at fuel and hot parts, and in the wiring at poor or aged connections. Shore power and chargers expressly belong on that list.
What puts it out
A dry powder extinguisher on deck or by the companionway, reachable without walking through the fire. For the engine space a discharge port, so the compartment need not be opened: air is exactly what the fire would then get. Plus a fire blanket in the galley.
The order in an emergency
Wake everyone and get them on deck, lifejackets on. Shut off gas and shore power, main battery switch off. Only then fight it, and if you can aim low into the flame, not at the smoke. Make the distress call in parallel, not afterwards.
Beforehand
Gas bottle in a locker that drains overboard, hoses dated and renewed every few years, extinguishers serviced and not buried behind the stowage. And once a year go through with everyone on board who shuts off what.
Choosing a fire extinguisher for a boat
Fires are classed by what is burning. Aboard a yacht that mostly means three things: solids such as cushions, timber and plastics, liquids such as diesel, petrol and oil, and gas from the galley. Cooking fat in a pan has a class of its own. A dry powder extinguisher rated for classes A, B and C covers the first three, which is why it is the standard choice on most boats.
Powder has a drawback worth knowing in advance. It spreads through the whole cabin, cuts visibility and attacks electronics and engines because it draws in moisture. That is no reason to hesitate when it matters, but it is a reason to reach for the fire blanket first when a small fire starts on the cooker. Foam leaves less mess and works on solids and liquids. Carbon dioxide leaves no residue at all, yet in a small closed space it also displaces the air you need to breathe.
As a rule of thumb, two handy extinguishers in different places beat one large one in a single spot. One belongs by the companionway or in the cockpit, the other near the forward cabin, so that whoever sleeps there can reach it without crossing the saloon. The number and size actually required depend on the country, the type of boat and where you sail.
Using a fire blanket on a boat
A pan of burning fat is where well meant help does the most harm. Water hitting hot fat flashes into steam and throws the burning fat upwards, and the flames reach the deckhead in an instant. Even a burst of powder from close range can blow the fat out of the pan. A fire blanket smothers the fire calmly by cutting off its air.
Mount the blanket within reach of the cooker but not directly above it, because that is where the flames go first. Once in place it stays there until everything has cooled, even if things look quiet after a minute. Lift it too soon and the hot fat often reignites as fresh air reaches it.
- Turn off the gas at the cooker and at the bottle if you can reach both safely.
- Pull the blanket out by its tapes and hold it so that it shields your hands and face.
- Lay it over the pan, moving away from yourself. Do not throw it.
- Leave it in place until the pan has cooled, and do not move the pan.
- Replace the blanket afterwards, as most are designed for a single use.
Fighting a fire on board with a portable extinguisher
A portable extinguisher empties faster than most people expect, often within a few seconds. That makes aim everything: the contents must reach the base of the flames, not the smoke above them. Get as close as the heat allows and discharge in short bursts.
Always keep a way out behind you. Below decks that means fighting the fire with the companionway at your back, never with the fire between you and the exit. On deck, stand with the wind behind you where possible so that smoke and powder blow away from you.
When the flames are out the job is not finished. Upholstery, insulation and wiring looms like to smoulder and flare up again later. Have someone stand by with a second extinguisher, open charred panels with care and use the back of your hand to feel where heat remains.
Engine and electrical fires: a boat fire below decks
An engine space fire often announces itself by smell, smoke from the vents or a temperature alarm. Stop the engine and shut the fuel supply. A running diesel draws in air and feeds the fire, and an open fuel line keeps supplying it. Then leave the hatch closed and discharge through the fire port, or trigger the fixed system if one is fitted.
After that the compartment needs time. Opening it straight away gives the fire fresh oxygen, and hot metal can relight the fuel vapour. As a rule of thumb wait several minutes before opening it carefully, with a second extinguisher ready in your hand.
Electrical fires usually start at joints: the shore power plug, battery and charger terminals, or cables that have chafed against an edge for years. Isolate shore power and the main battery switch first. Lithium batteries, whether house banks, power tools or e-bikes, are a hazard of their own. Once they go into thermal runaway they keep heating themselves and an ordinary extinguisher will barely touch them. Distance and large amounts of cooling water are then the only real options.
Preventing fire on board and making the distress call
Bottled gas is heavier than air and settles in the bilge. A gas alarm with its sensor just above the floorboards, the habit of closing the bottle valve after every meal, and regular inspection of the installation by a competent engineer remove most of that risk. A smoke alarm in the saloon and a carbon monoxide alarm near the berths cost little and will wake you before you notice anything yourself.
If a fire is not quickly under control, the boat and the people aboard are in grave and imminent danger, and that is a Mayday. On a DSC radio, send the distress alert first with the red button. Then follow with the voice call on channel 16: Mayday three times, the boat name three times with call sign and MMSI, then Mayday once more with the name, position, nature of the distress, help required and number of people aboard. Operating a marine VHF requires a licence, which at sea is the Short Range Certificate, the SRC.
If the fire is out but you still need help, perhaps because the engine is now dead, a Pan-Pan urgency call is the right choice. If the fire cannot be held, everyone leaves with lifejackets on, from the windward side, so that smoke and flames blow away from the liferaft.
Frequently asked questions
Which fire extinguisher is best for a boat?
For most boats a dry powder extinguisher rated for classes A, B and C, together with a fire blanket in the galley. If you want to spare sensitive electronics, carry a foam extinguisher as well. Being able to reach it without a detour matters more than the make.
How often should a marine extinguisher be serviced?
Follow the manufacturer's service interval and have it checked by a competent service company. In between, check the pin, the pressure gauge and the hose yourself. Powder can compact with the constant motion of a boat, so turning the unit over now and then does no harm.
Can I use seawater to put out a fire?
On burning wood, cushions or fabric, yes, and there is plenty of it. Never on fat, fuel or live electrics, because water spreads the fire or conducts current.
What should I do if a boat catches fire in the marina?
Get everyone off, call the fire service and the harbour office, and warn your neighbours. A burning boat can break free or set others alight. Isolate shore power at the pontoon if that is safe, and do not go below alone to fight it.
Is a gas alarm worth fitting on a small boat?
Yes, on any boat with a gas installation. The sensor goes low down, where escaping gas collects. Test it at the start of each season following the maker's instructions.
What this has to do with insurance
Fire is covered under hull insurance, and the effort is still worth it: after a fire a boat is usually a total loss, and what is replaced is the value, not the boat with its history. Check as well whether your agreed value still matches today's replacement cost, because that is exactly when it applies.
