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Published: January 2014

Extinguishing Doubt

Photo of a fire extinguisher pressure gauge

The time to know if your fire extinguishers work is not when you are about to use them. This winter, make sure your extinguishers are up to snuff.

Most portable fire extinguishers are nonrechargeable and contain powder that may compact over time, which can make them useless in an emergency. Once or twice a year, remove your extinguishers from their brackets and vigorously shake them to break up the powder. If it's been a while, you may need to hold them upside down and strike the bottom with a rubber mallet (don't use a hammer because it might chip the paint and allow the canister to corrode). If you can't feel loose powder inside the canister, it's time to replace it. Mounting the extinguisher horizontally will often delay the chemical from packing, but they still need to be shaken.

Most portable extinguishers have a pressure gauge that should also be checked at least twice a year — the reading should be in the green zone. If it's not, less expensive fire extinguishers will need to be replaced. Some more expensive portable fire extinguishers can be recharged if the pressure gauge is no longer in the green. Those types should be serviced annually by a qualified extinguisher company, who will tag them with the date of service. Also check for dents and corrosion, and make sure the nozzle hasn't gotten damaged. Nonrechargeable fire extinguishers don't last forever and have expiration dates, usually 12 years from the date of manufacture.

Fixed engine room systems that contain halon or FE 241, should be inspected twice a year, and the canisters should be weighed annually to see if they've lost any of their charge. If so, they need to be serviced and recharged.

Cause Of Fire: Bilge Pump

Photo of a burnt bilge pump

You put a bilge pump aboard to protect your boat, and for the most part, that's exactly what it does. But every year Seaworthy gets reports of bilge pumps smoking, melting, and even starting fires. The problem is caused by a combination of incorrect fuse size and something called rotor lock, a condition in which the bilge pump rotor can no longer spin because it's jammed with debris or bilge scum, or the bearings are seized.

Here's what happens: A locked rotor causes the 12-volt wires to heat up, which should blow the fuse. But a fuse rated for more current than what the manufacturer calls for may not blow even if the wires get hot. The hot wires create even more resistance, which decreases the current flow in the wires, preventing the fuse from ever blowing. Because electricity is still flowing, the wires start to smoke and eventually glow red-hot, at which point they could ignite anything flammable nearby.

Many small bilge pumps call for a 3-amp fuse, but sometimes installers substitute a 5-amp fuse because they're more likely to have one lying around. It's critical to install the exact fuse size manufacturers recommend for use with their bilge pumps — a fuse rated even one amp higher could lead to a fire if the rotor locks. Also, make sure the wire size to the pump is correct — too small of a wire can also overheat without the fuse blowing.

Fiberglass And Ethanol Don't Mix

Photo of a ethanol damaged tank
Photo: Garry Peckham

Or rather, they do mix, too well. Gerry Peckham shared this photo of the fiberglass fuel tanks from his 28 Bertram FB. After having multiple fuel filter and fuel pickup tube clogs, he decided it was time to replace the fiberglass tank with a new aluminum tank. Upon cutting open the old tank, the damage E10 (gasoline with 10 percent ethanol) was causing to the internal surfaces was obvious.

Independent laboratory tests sponsored by BoatUS Marine Insurance in 2006 confirmed that the resins used in some fiberglass tanks were leaching from the tank walls, weakening the tanks. The resin makes its way through the fuel system where it sticks to valves and other internal engine parts. The buildup of this sticky black substance has bent pushrods, clogged intake valves, and ruined some engines. Affected engines may run rough, stall, or bog down under load.

The majority of gas tanks on boats are made from either aluminum or plastic. However, some older boats, mostly high-end sportfishers, were built with fiberglass gas tanks. On newer boats, some smaller, portable, and under-the-seat gas tanks are also made from fiberglass. Though custom and semi-custom yachts may also have fiberglass tanks, these typically use diesel rather than gasoline, and so are not affected.

Anyone who owns a gasoline-powered boat and runs on E10 should inspect the fuel system regularly to head off E10-related problems. And if that boat has fiberglass tanks, consider it a prime candidate for tank replacement.

Hidden Chainplate Dangers

Photo of a chainplate
Photo of FLIR image of chainplates
Photos: Dylan Bailey

Seaworthy has often warned of the dangers of crevice corrosion on stainless steel chainplates, especially where they pass through the deck and cannot be inspected. As a boat ages, it is almost impossible to prevent saltwater from leaking down through the chainplate cover. If it becomes trapped against the chainplate in an area with little or no oxygen, it can lead to crevice corrosion that will eventually cause the chainplate to fail. Most riggers recommend inspecting the parts of the chainplates that can be seen annually and pulling them from the boat for a complete inspection and possible replacement every 10 to 12 years.

This kind of corrosion cannot occur if stainless steel in oxygen-starved areas stays dry. In the '70s and '80s, a number of sailboat manufacturers began completely encapsulating the chainplates in fiberglass to prevent water from intruding and causing corrosion. Some older boats, like Ericson and Irwin, as well as many of the Taiwanese-built boats, have encapsulated chainplates. As these boats age, the chance of water leaking into the encapsulated area and coming into contact with the chainplates increases. The chainplates can neither be inspected nor pulled without destroying a great deal of fiberglass. Some builders still use encapsulated chainplates, though most have drainage holes designed to keep water from being trapped against the metal.

As a quick search on the Internet will show, failure of these chainplates is far from uncommon. The chainplate above came from a 1987 Irwin — crevice corrosion had succeeded in penetrating halfway through the plate. Luckily it was replaced before it failed. Thermal imaging offers a window into these hidden areas and may assist boaters in determining whether or not water has become trapped around chainplates. The cooler blue color at the bottom of the lower image shows lower temperature below the base of the chainplate that likely indicates moisture.

If you're in the market for an older sailboat, find out whether or not the chainplates are encapsulated and weigh that into your buying decision. If you already own a boat with encapsulated chainplates, you may want to consider thermal imaging to see if they need to be replaced. But if the boat's in its third or fourth decade, you're probably better off just replacing them — as painful and time-consuming as that can be. You'll find lots of descriptions of how others have gone about it on the owner's forum of whichever boat you own.End of story marker


Seaworthy, the damage-avoidance newsletter, is brought to you by the BoatUS Marine Insurance Program. For an insurance quote, please call 1-800-283-2883 or apply online at


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