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Old 07-14-2003
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Fire on Board!


About the worst thing that can happen on board a boat is a fire. The good news is that most blazes can be readily prevented.
The concept of a fire on-board is so frightening that most sailors tend to banish it from their thoughts. If the nagging worry ever does penetrate our consciousness, maybe we check the gauges on the fire extinguishers. After all, what else can we do?

Plenty.

Not every fire is preventable, but most are. Giving your boat a fire risk check-up will help you identify conditions that could lead directly to a fire. And spending an afternoon thinking about the unthinkable could save your boat, or even your life.

So let's start with the galley. According to insurance statistics, the majority of boat fires start in the galley. An astonishing number stem from alcohol stove flare-ups. That makes the real cause haste—trying to get a pressurized stove going without sufficient preheating. Never attempt to save time (or alcohol) by underfilling the priming cup. If you are committed to alcohol as your cooking fuel, an excellent fire-prevention strategy would be to switch to a stove that is not pressurized.

Propane stoves intended for boat use have safeguards to prevent flare-ups, which happen explosively with propane. A thermocouple at each burner prevents the flow of gas when it fails to sense a flame. While lighting the burner typically requires holding the valve open manually for a few seconds to give the flame time to heat the sensor, under no circumstances should you otherwise bypass the thermocouple.

Propane stoves are also equipped with igniters. If a burner begins to ignite with a pop and a flare, the problem may be the igniter or the flow of gas. Either way the stove must be serviced immediately to correct this condition before this small explosion becomes a big one.


The galley is one of the points of origin for many on board fires, and most of those come from grease.

A grease fire is also a galley risk—as in any kitchen. To guard against this possibility, which can be minimized by vigilance on the part of the cook, there should never be anything readily flammable above the stove. On board, curtains come to mind.

The good news about galley fires is that they are invariably detected immediately, providing the opportunity for immediate action before the flames spread. If you have a galley fire of any kind, first turn off the burner to stop the flow of fuel. If your boat is properly prepared, you should be able to reach a fire extinguisher from either side of the stove. That means you need at least one extinguisher mounted forward of the galley and one aft. If you have to reach over the stove or even over the countertop to reach an extinguisher, move it to another location.

Never hesitate to use a fire extinguisher because of the mess it is going to leave behind. That said, there are less messy options for snuffing a small fire if you have prepared in advance. Nothing puts out a pan fire quicker than smothering it. A wet towel can do the job, but you cannot let the fire burn while you wet a towel. Fire equipment suppliers sell treated blankets that—if immediately at hand—can knock down a small galley fire quickly and cleanly.

After you've made the galley secure, it's time to prevent against electrical fires because these are nearly as common as galley fires, and they are typically more insidious. An electrical fire tends to start in some hidden part of the boat, not becoming apparent until it has ignited flammable stores or the boat itself.


Worn or corroded wires are another prinicipal cause of on board fires, but regular inspection can help lessen the possibility of an electrical flare up.

High resistance—in the form of a loose or corroded connection or broken strands—is invariable the cause of electrical fires. To understand the physics at play here we use the power loss formula P= I2R, where P is power in watts, I is current in amps, and R is resistance in ohms. If you have a 10-amp current flowing through a corroded connector that offers 10 ohms of resistance, you have the equivalent of a 1.000 watt heating element.

Corroded connections are often right there for you to see if you just bother to look for them. As part of your annual fire prevention, take a powerful light and shine it on every wire connector in the boat. If you see any signs of corrosion, disassemble and clean the connection. If the connector is in bad shape, replace it.

Next, switch on all of the boat's 12-volt equipment, and then make a second pass through the boat laying a fingertip against all connectors and all exposed wire runs. Be sure the shorepower is disconnected and the inverter is turned off when you are doing this. You are looking for connections or wiring that feels warm to the touch. A clean connection should not cause heat losses. The same is true for wire that's big enough for the job. If you find anything warm, take corrective measures. And while you are doing these inspections, make sure that no paper products, cloth, plastics, fuel or other easily ignited materials are, or could be, lying against the wiring or the connectors.

"The biggest contributor to electrical fires is the absence of a fuse in the circuit. If an unfused circuit shorts out, the current can surge to hundreds of ampssufficient to ignite most flammable substances."
The biggest contributor to electrical fires is the absence of a fuse in the circuit. If an unfused circuit shorts, the current can surge to the hundreds of amps. A wire intended for fewer amps will offer sufficient resistance to become hot enough to ignite adjacent flammables. Circuits emerging from the breaker panel are protected, but those connected directly to the battery too often are not. Items that might be connected directly to the battery include solar panels, wind generators, battery chargers, automatic bilge pumps, radios, and battery monitoring devices. Every one of these must be fused close to the positive battery terminal. The one exception used to be the starter cable, but today fuses suitable for this high current circuit are readily available at modest cost. If you find any wire, including the starter cable, connected to the battery without protective fuse, install one.

Now we come to engines. Gasoline-fueled powerboats regularly experience catastrophic engine-room fires. These are mostly preventable with properly installed tanks and fuel lines, and with the installation of bilge blowers. Of course meticulous engine maintenance and careful fueling and starting practices will also help you avoid engine fires.

Fortunately gasoline engines, other than outboards, have not been installed in production sailboats in about 25 years. Diesel engines rarely start a fire, and when this does happen, a worn fuel line is the usual culprit. Make sure fuel lines runs are clear and not at risk of rubbing against anything.

If your boat has a gasoline engine, or if you just want a higher level of fire protection for the engine compartment, you should consider fitting it with an automatic extinguisher. The cost is less than $200 to protect a 100-cubic-foot compartment. An automatic extinguisher provides the considerable advantage of nearly instantaneous fire response, often extinguishing the fire before the crew is even aware of its existence.


It's imperative that propane tanks and lines be properly stowed, installed, and inspected. Always ensure that the propane locker drains overboard.
Another major fire hazard stems from the improper storage of propane. A proper propane locker must be isolated from the interior of the boat and must drain overboard, but not near any opening that could let the gas enter the interior of the hull. Propane lines running through the boat are also a potential risk if they fracture or wear through. Give your propane installation a thorough safety check and correct any deficiencies that you find.

While we're on the subject of fuel, every sailor should know that storing gasoline in an interior locker is a risky practice. Keeping jerry jugs on deck may be less attractive, but it is a much safer option. And don't keep oily rags aboard. Not only will they fuel a fire, but also under the right conditions they can actually spontaneously combust. Charcoal presents a similar risk when it gets damp. If you must take charcoal aboard, seal it in plastic bags to keep it dry.

Lightning can also set your boat on fire, but that is unlikely to happen if you provide the bolt a continuous route to ground. Make sure your mast is bonded to an underwater ground plate with heavy copper strapping or No. 4 AWG cable. The straighter the path to ground, the better, so the ground plate should be more or less directly beneath the mast. Do not ground the mast through the engine. This likely increases the risk of fire rather than lowering it.

"A small fire extinguisher will be completely discharged in about 10 seconds."
Because prevention is the best approach to keeping your boat fire-free, I recommend that you follow these prescriptions: Have an adequate compliment of fire extinguishers aboard. That likely means more than the Coast Guard requirement. Be mindful that a small extinguisher will be completely discharged in about 10 seconds. Personally, I want more than 20 or 30 seconds of fire-fighting capacity.

Maintain your extinguishers. That means turning them upside down and shaking them vigorously every six months. If you can't get the powder to move around inside, it is packed in the bottom and the extinguisher is probably useless. The gauges on inexpensive extinguishers sometimes lie. You should weigh extinguishers at least annually. If the actual weight is not within a quarter pound of what is on the label, replace the extinguisher.

If you use propane aboard, equip your boat with a propane detector. These so-called sniffers detect propane inside the boat before concentrations rise to explosive levels. Your propane installation should also include a pressure gauge for leak detection. Considering the danger of propane leaking into the bilge, I would not consider leak testing on a weekly basis to be overkill. And I also favor the installation of an ignition-protected bilge blower when propane is used aboard. Should propane somehow leak into the interior of the boat, you can bail it out with a bucket, or even pump it out with a manual bilge pump, but you are going to be holding your breath in fear of an explosion the whole time. A blower definitely provides quicker relief.


Of course boundless supplies of water are always on hand for fighting on board fires, but you've got to have the means to get the water to the fire.
And finally, keep in mind that boats have an inexhaustible supply of water immediately at hand. A deckwash pump can double as a fire pump if you have it connected to a long hose. However, you should not spray water on a petroleum fire—the oil floats on the water and spreads the flames—but a spray of water can protect or extinguish virtually all other onboard combustibles. Damage from spraying seawater below will be far less than what would have otherwise resulted from the fire you extinguish.

So prepare yourself and you can successfully combat an onboard fire. Prepare your boat and you should never need to face one.

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