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Muskrat Love Gone Bad

Photo of a Muskrat and a Sunken Boat Hull

Nature's little troublemaker.

As a BoatUS Member from Alexandria, Virginia was watching a yard worker power-spray the bottom of his boat prior to winter lay up, a family of four muskrats hopped out of his boat's exhaust and waddled indignantly across the parking lot and jumped into the water. It was quite a surprise for the Member and even more of a surprise for the yard worker, whose face was only inches away from the flying rodents. After making there were no more surprises, the Member peered into the exhaust and found grasses, oyster shells, assorted crab parts, and — no one can explain this — a Phillips head screwdriver. He also found a large hole had been chewed in the exhaust just above the waterline. The Member has since vowed to visit his boat more often.

Muskrats usually make their homes by burrowing a few feet into marshes and riverbanks and then building a nesting area just above the waterline. Sound familiar? The long, dark passage in a boat's exhaust must be business as usual for a muskrat, at least until someone starts the engine. Just what goes through their heads when they hear a loud rumbling and smell smoke is anybody's guess, although it doesn't appear to cause much concern.

A muskrat living in a boat's exhaust near Seattle, Washington didn't budge when the owner fired up the twin 6-71 diesels, let them idle for 20 minutes, and then shoved the throttle forward for a 40-minute run to a marina. It wasn't until the boat was hauled out ashore that the muskrat, covered with soot, reluctantly dropped to the ground and waddled quickly back to the water. (Muskrats can tolerate noise and soot but they clearly don't like being away from water.) Like its counterpart in Maryland, the muskrat had chewed a hole in the exhaust just above the waterline, which, given a little more time, could easily have sunk the boat.

Photo of the Muskrat Damage

The muskrat's handiwork.

Jane Christen, a marine surveyor in Washington State has investigated many claims for boats that have been damaged or even sunk by a lot of different rodents, but none that are quite as persistent as muskrats. The question for anyone who owns a boat near muskrats, which is just about everyone, is how do you keep them out of your boat's exhaust? Jane says that in New England, she's heard that commercial fisherman place paint cans with over the exhausts with lines into the cockpit. The latter is used to pull out the cans whenever the engines are started. Other skippers have tried devising screens to fit over exhaust openings. As a more shipshape alternative, or when exhausts are hidden beneath swim platforms, Jane recommends "Muskrat guards" sold by Dunato's (206-547-7852) in Seattle. A Muskrat guard installs in an exhaust with threaded bars that can be adjusted to hold it firmly in place. At $245 to over $400, depending on the size of your exhaust, they're pricey but a lot cheaper than replacing your boat.

Note: Marine insurance policies typically exclude damage caused by "vermin," which includes muskrats. If a muskrat chews through an exhaust hose, the BoatUS policy will pay for consequential damage caused by the sinking, but not for the damage to the exhaust hose itself. If your boat isn't insured by BoatUS, check your policy language or check with an underwriter.

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Bob Adriance

Contributor, BoatUS Magazine

Bob Adriance is the former editor of Seaworthy, which is now incorporated into BoatUS Magazine and called BoatUS Reports. The stories and lessons learned are based on real-life BoatUS Marine Insurance claim files.