How to Winterize an Outboard Motor

1. Stabilize the fuel, then run it through

Ethanol-blended gasoline starts absorbing water and losing combustibility within weeks, and a motor that will sit for five months is the classic casualty. Fill the tank first — a nearly empty tank sweats condensation all winter — then add fuel stabilizer to the tank at the rate on the stabilizer label and run the engine for ten to fifteen minutes so treated fuel replaces untreated fuel in the lines, filter and injection or carburetion system. On direct-injection engines, running the engine is what circulates the treated fuel, so do not skip it.

2. Change the oil while the engine is warm

Warm oil drains freely and carries suspended contaminants out with it; cold oil leaves them behind. Run the engine for a few minutes to warm the oil, then drain it and replace the oil filter. Check what came out: a milky, coffee-with-cream colour means water has entered the oil, which is a diagnosis worth acting on before storage rather than in spring.

3. Fog the cylinders

The goal is a film of oil on the cylinder walls so they do not rust while the motor sits. On most four-strokes that means spraying fogging oil into the intake or into the spark plug holes, then reinstalling the plugs. Many two-strokes are protected by mixing fogging oil into the fuel and running it in. Procedures differ by model, so follow the method in your manufacturer’s manual and use the plug and wire handling it specifies.

4. Drain every pocket of water

Water is what actually cracks a block. After flushing with fresh water following salt or lake use, tip the motor so water leaves the powerhead, lower the unit if the boat is on a trailer, and drain the fuel filter and water separator into a container. Confirm the anti-ventilation plate and gearcase are not sitting in a puddle of trapped water in the boat.

• Flush with fresh water if the motor ran in salt or brackish water.
• Drain the fuel filter and water separator — the usual first source of spring starting trouble.
• Leave the motor tilted or trimmed so water drains out rather than settling in.
• Do not store a motor with water standing in a block or manifold.

5. Gearcase oil, grease and sacrificial zincs

Change the gearcase oil at both ends of the lower unit; gearcase oil that comes out milky tells you a seal has failed and water is getting in. Re-grease the swivel and pivot points so the tilt and trim mechanism does not seize, and inspect the sacrificial anodes. Anodes that are more than half wasted should be replaced before the next season, not after.

6. Battery, controls and cover

Pull the battery, charge it fully and store it on a maintainer in a dry place away from freezing, or accept a shortened battery life. Work the steering and shift controls through their range and check the terminals. Cover the motor with something breathable; a plastic tarp that traps moisture does more harm than good, and a closed engine compartment invites condensation and rodents.

What winterizing does not cover

Winterizing is maintenance, not warranty work. Outboards sold here carry the applicable manufacturer’s warranty only, and warranty obligations are limited to what that manufacturer’s printed literature or website describes. Repairs run through authorized dealer networks, and inspection or repair can require transporting the motor to a service center at the purchaser’s cost. Identify your closest authorized service center before you need it.

Questions boaters ask