This Invasive Mollusk Could Destroy Your Boat’s Engine

Proper boat maintenance requires time, patience, and money. As with a car, owners must check the oil. They also need to monitor the battery and electric systems, assess the steering movement, and examine the hull and propeller for damage. Plus, they should mitigate the risk of damage caused by aquatic species.

One particularly destructive species, the zebra mussel, can cause extensive hull and motor damage if boat owners don’t take proper precautions and perform the appropriate maintenance.

What are zebra mussels?

Zebra mussels are a freshwater species of mollusk that originated in Russia and Ukraine. They’re so named because their shells often feature dark zigzags. These shelled creatures can range in size from a quarter-inch to as large as two inches. Zebra mussels can live up to five years, and females can produce as many as a million eggs a year. That means a small infestation can grow rapidly. Since the 1980s, zebra mussels have been found in states such as Texas, California, and Colorado, the Great Lakes region, and other parts of Europe.

Zebra mussels are filter-feeding organisms. They feed by opening their shells and taking in water, from which they filter out nutrients. Through this process, the mollusks can also remove pollution from the water, which can increase water clarity and sunlight. As a result, submerged aquatic plants often grow faster, increasing the food supply for bottom feeders. However, the overgrowth of these plants can cause water-quality issues.

The zebra mussel counts dozens of bird and fish species as its natural enemies, although most don’t reside in North America. Two notable predators are crayfish and smallmouth bass, which consume significant numbers of zebra mussels daily.

How do zebra mussels damage boats?

Zebra mussels attach themselves to layers or substrates, including aluminum, fiberglass, steel, and wood. Their microscopic larva — veligers — prefer hard substrates, such as a boat’s surface). Often, they find their way into a boat engine’s passages and attach themselves where they may remain as they grow.

According to the Wisconsin Department of Natural Resources, growing zebra mussel colonies can be found on a boat’s anchor, hull, trailers, chains, and other equipment. They can also be found in an engine’s cooling system, internal passages, hoses, and other passageways, where they can compromise a boat’s mechanical functions. Because of the mollusks’ initial microscopic size, boat owners often are unaware of the unwanted passengers until they overheat a motor or compromise water pumping capabilities.

Before taking a boat into a new body of freshwater, boat owners should check to see whether water authorities have determined a high concentration of zebra mussels. If so, the best strategy to prevent related damage is avoidance. However, there are ways to protect a boat from these pesky bivalves.

How you can protect your boat from these destructive creatures

To make the most of boat ownership and avoid expensive repairs, boat owners should always start with visual inspections because adult zebra mussels are visible to the naked eye. Owners should also clean their boats with fresh water, ensuring they thoroughly cleanse all open passages and crevices in which adult and juvenile mussels might reside. These mollusks can survive outside of water only for about a week, so letting a boat dry for that period can rid it of any remaining intruders.

Boat owners can also run their bats at slow speeds to kill colonies, as the rising temperatures in the engine cooling system prove intolerable to zebra mussels. Motor flushers (or motor muffs) can also be helpful because they flush away foreign particles, including mussels, from engine components. And applying anti-fouling paints to the hull and engine cooling system can prevent mussels from latching on.

Finally, store the boat on a lift when not in use. A moored boat should have its motor raised so that zebra mussels can’t find their way into the intake grate. Further, all water should be discharged after an outing because the water might contain mussels or veligers. And any aquatic plants or debris should be removed from all components for the same reason. 

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