Winter outboard maintenance

Don't store the boat just yet—follow these 8 steps to winterize your outboard first

By David HarrisDavid Harris


Photo by Eden Robbins

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Think the procedure through: End-of-season tasks should be done in a specific order.

1. Add fuel stabilizer to the fuel tank

Run the engine for a few minutes to circulate the stabilizer.

2. Change the oil and filter in four-stroke engines

An oil change can be done with the engine still mounted to the boat in the water; however, it is easier and tidier if you do the job out of the water. Not only will you save your back, you’ll eliminate the risk of dropping tools or spilling oil into the lake.

Out of the water, warm up the engine to operating temperature so that the oil will drain well. In this instance, you’ll need to provide a cooling water supply using rubber “earmuffs,” a device that clamps around the lower unit and attaches to a garden hose, allowing you to run the engine out of the water (above, left). Earmuffs are widely available and worth the moderate investment). Once the engine is up to temperature (hot to the touch), shut it down, then remove the drain plug — careful not to lose it. The oil will be hot, so collect it by funnelling it into a sealable container. When the oil stops dripping, replace the drain plug and remove the oil filter. Be sure to catch the drips. Replace the filter before refilling the engine with new oil, as per the manual. Run the engine for a few minutes, then recheck the level at the dipstick.

3. Fog the engine

Engine storage spray is a rust-inhibiting preservative that coats the internal components from the air intake through the combustion chamber and the exhaust. With the engine running at a quick idle, squirt the spray into the air intakes (right) as per instructions on the can or until a “fog” comes out the exhaust, then shut the engine off.

4. Drain the engine of water

Set the engine up on a stand so it’s vertical and stable. Gravity will do most of the work and water will drain out of the lower unit. It helps to turn the motor over by hand: Remove the spark plugs, then pull the start cord gently to eject the last drops.

5. Drain the carburetors (for engines without fuel injection)

A small drain screw is usually located on the bottom of the fuel bowl. Remove it and collect the small amount of gas that drains out, then replace the screw.

6. Drain and replace the lower-unit gear oil

Milky gear oil means water has got in through the prop shaft seals, which should be replaced. If water is getting in, oil is getting out — time for a visit to your marine mechanic, as failure of the gears is not a cheap prospect. First, remove the upper vent screw, then remove the drain/fill screw, allowing gear oil to drain into your container. Refill at the fill hole with the proper grade of gear oil until it flows out of the upper vent hole. Install the upper vent screw (three hands help here). Quickly remove the bottle and install the drain/fill screw. Note there should be a nylon washer on each of these screws to prevent leaks.

7. Lubricate any moving parts

It is best to store the engine in an upright position. If the engine must lie down, check your manual; some four-strokes can only be stored on one side, otherwise engine oil will drain out over the winter. Yuck.

8. Remove, store, and charge battery

A well-maintained battery should see you through five or six seasons.

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David Harris