How to Winterize a Boat Motor

by Will Charpentier
Properly winterizing your motor is essential to keeping it running.

Properly winterizing your motor is essential to keeping it running.

With winter's freezing temperatures, your boat faces more challenges than your car. Your car's motor gets a workout almost every day, but your boat doesn’t. Protecting your car's engine from the cold may be as simple as adding antifreeze to the cooling system. Winterizing your boat's motor, on the other hand, is all about water removal and you should winterize the motor’s drive, cooling and fuel systems, in that order.

Safety First

  1. Before you begin to winterize your boat’s motor, remove the negative battery cable from the battery. You’ll need a 5/16-inch wrench to loosen the nut on the negative lead. You should also remove the propeller from the propeller shaft. Send the propeller to a prop shop for repair and refinishing.

Lower Units and Outdrives

  1. Water that freezes in your motor’s drive can wreak havoc with the drive system of both inboards and inboard-outboards. The water gains access to the drive unit of an outboard motor through faulty water pump seals or prop shaft seals. Changing the lower unit or outdrive oil prevents this. When you drain the oil, look at the color. If it's milky, you have a broken seal that's allowing water to leak into the drive system and the seal needs to be replaced. Feel the oil -- rub a bit of it between your fingers. It shouldn't feel gritty. Some very fine metal particles in the oil are normal and usually aren't noticeable. Gritty lower unit oil means abnormal gear wear.

Cooling System

  1. Your boat and engine operating manuals tell you the type of cooling system your motor uses. Almost all outboards rely on a raw-water cooling system. The intakes for the system are underwater when the boat’s in the water. The intakes pull water into the engine's water pump for distribution throughout the engine. Winterizing these system means cleaning the strainers on the inlet ports. You must replace an outboard motor’s water pump outdrives as part of the winterization process.

    Some outboard motors and most inboard-outboard motors use closed cooling systems like the one in your family car. Winterizing closed systems such as these requires you to bleed the system and replace the antifreeze/water mixture with straight antifreeze, just as you do with an automobile.

    After you finish winterizing your motor completely, open any water drains shown in the operating manual. Crank the motor for 5 seconds to blow any residual water out of the cooling system.

Fuel Systems

  1. Change the fuel filters when you winterize your motor. Most boat motor manufacturers recommend you change fuel filters every 500 hours or once a year. Cold temperatures cause the residual fuel in filters to gum up. If water trapped in the filters freezes, the filter expands and can damage fuel lines.

    If your motor has a carburetor, connect the motor to a water supply, according to the instructions in the motor operator manual. Spray fogging oil -- available at boat supply houses -- into the carburetor and disconnect the engine's fuel supply. Continue to spray the fogging oil until the engine stops. This protects the carburetor, the cylinders and the exhaust system.

    Fuel-injected engines lack a carburetor. Instead, when you fuel your boat throughout the season, add one ounce of fuel stabilizer for every gallon of fuel you add. This isn't necessary for outboards, but it's a good practice, anyway. Use any gasoline left in the fuel tank for yard equipment; it won’t keep over the winter.

Automated Winterization

  1. Evinrude's E-TEC series outboards feature a self-winterization feature. You connect the outboard to a water source, start the engine and move the throttle to the high-idle-winterization throttle position. The motor's speed will vary and the engine will shut down after about 30 seconds, fully winterized. Whether this feature will eventually appear in other outboard motors remains to be seen. In the meantime, your motor’s operator manual contains all the manufacturer’s recommendations on preparing your motor to endure winter's inactivity.

About the Author

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.

Photo Credits

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