How to Winterize a Four-stroke Boat Engine
Whether a four-stroke outboard, or a four-stroke inboard-outboard with a stern drive, all boat motors have needs at the end of the boating season. The process is called "winterization." Prepping your motor for its long winter nap ensures your motor will survive the colder winter months undamaged and stand ready to take on the challenges of the next boating season.
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Instructions
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1
Add fuel stabilizer to the fuel tank on your last outing. This allows the fuel stabilizer to move through your whole fuel system. Fill your tank after you haul your boat out of the water and add stabilizer to the fresh tank of fuel according to the directions on the fuel stabilizer.
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2
Open the drain plugs on the raw water cooling system by turning the plugs counterclockwise with a wrench. Drain any water from your engine. After the water drains completely, close the drain plugs.
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3
Fill the raw water cooling system with rust-inhibiting propylene glycol anti-freeze, the kind used in recreational vehicles (RVs). If your cooling system is a "closed" system, relying on a keel-cooler radiator on the bottom of the boat, mix the antifreeze with water: half water, half antifreeze.
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4
Spray 2-cycle fogging oil into the carburetor, if your engine is equipped with a carburetor. It's not necessary that your engine run while being fogged, since you've already introduced fuel stabilizer into the fuel system. Dust the rest of the engine with fogging oil.
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Lower your motor, if an outboard, or your stern drive, if your boat is an inboard-outboard. Outboard motors should always be stored upright, so that oil doesn't run into the cylinders and stern drives should be lowered to prevent the bellows at the base of the stern drive from becoming deformed.
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Tips & Warnings
An oil change might be considered, but oil changes are better left until spring fitting out, so the oil is fresh at the beginning of the season.
Antifreeze is toxic to pets and small animals. Take appropriate precautions when adding or removing antifreeze from your boat's motor.
