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Causes of Boat Fires

What the claim files teach us about preventing boat fires.

Fire ranked number five among the causes of loss for BoatUS Marine Insurance between 2008 and 2012. The majority of these fires start in a few very specific places aboard, with many of them originating in the engine compartment where fuel and an ignition source have a high likelihood of coming together. Maintaining your boat well, particularly with respect to the electrical and fuel systems, is the best way to prevent fires aboard. However, there are five specific areas that lead to most of the fires we see in our claim files. If every boater paid attention to these five things, we could prevent a third or more of all fires aboardboats.

Off-Boat Sources (26%)

More than a quarter of the time, our insured's boat burns when something else goes up in flames — the marina, the storage facility, the house, the garage, the barn, the neighbor's house. In more than 70 percent of those cases, it's the marina that burns. A high percentage of those fires start on someone else's boat. That means that every boat owner has a responsibility to prevent fires on board, not just to keep his or her boat safe, but also to keep the people, boats, and property around it safe.

Engine Electrical (20%)

Wiring harnesses and starters cause a disproportionate number of fires on boats more than 25 years old. If you have a vintage boat and those parts are original, consider replacing them. Most of these older boats had relatively simple wiring harnesses, so if the manufacturer is no longer in business, or the part is no longer available, a good electrical technician can put one together for you.

Other DC Electrical (15%)

While loose battery connections, chafed battery cables, and aged battery switches can all cause fires aboard, the most common cause of battery-related fires is operator error: reversing the battery cables or connecting them in series when they should have been in parallel, or vice versa. If you're disconnecting your batteries for any reason, photograph the configuration with your phone first, label the battery cables, and mark the positive lug with red fingernail polish to make sure you avoid a shocking experience when you reconnect them.

AC Electrical (12%)

Bringing air conditioning, microwaves, electric heaters, and other AC appliances aboard makes life on the dock more comfortable and convenient but also greatly increases the risk of fire. Most AC electrical fires start somewhere between the marina pedestal and the shorepower inlet on the boat. BoatUS has long recommended using only marine-grade power cords with proper adapters and replacing them at the first sign of wear on the cord or pitting on the blades of the plug. But the analysis of our fire claims has identified another high-risk area on boats more than 10 years old: the back of the shorepower inlet where the ship's wiring connects to the terminals. Replacing the shorepower inlet on older boats if it is original, or at least pulling it out and inspecting the connections, could well save your boat.

Other Engine (9%)

Any interruption of cooling water can lead to overheating and then to a fire. In this case, a blockage of the raw-water intake caused the overheating. Other exhaust fires are caused by impeller failures due to age or to sediment in the water. If your engine overheats, check the engine compartment before getting underway again. Change your impeller every other year, and after a grounding, or operating in particularly dirty waters.

Batteries (8%)

On older outboards, the voltage regulator is by far the most common cause of fires. The failure rate increases with age after 10 years, so if your outboard is 15 years old or more, replacing the regulator may well keep you from having a bad day on the water.


Beth Leonard

Contributor, BoatUS Magazine

Beth Leonard is the former technical editor of BoatUS Magazine.