How to Winterize an Outboard Motor (and Year-Round Outboard Maintenance)

How to Winterize an Outboard Motor (and Year-Round Outboard Maintenance)

To winterize a four-stroke outboard motor: stabilize the fuel and run it through the engine, flush a water-cooled model’s cooling system with fresh water, change the engine oil and filter where fitted, change the lower unit gear oil, fog the engine if the manual calls for it, grease the fittings, then store the motor upright or tilted down so all the water drains. Always follow the owner’s manual for your model, because procedures vary between carbureted and fuel-injected motors.

Cooling-system flushing and telltale checks apply to water-cooled outboards. Honda’s BF2.3 uses forced-air cooling and has no water pump; follow its own cleaning and storage instructions. See Honda’s BF2.3 cooling details and choose the matching serial range from Honda’s BF2.3 owner’s manuals.

Step-by-step: how to winterize an outboard motor

1. Stabilize the fuel. Add a marine fuel stabilizer to the tank, then run the engine long enough for treated fuel to reach the fuel system. On small carbureted motors, the manual may recommend draining the carburetor instead.
2. Flush the cooling system. For water-cooled models, run fresh water through the engine with a flushing attachment or the motor’s flush port, as the manual describes. This removes salt, silt and debris that cause corrosion.
3. Change the engine oil and filter. Used oil contains acids and moisture that can corrode internal parts over the winter.
4. Change the lower unit gear oil. Drain it from the bottom plug and look at it. Milky gear oil means water is getting in, and a seal should be checked before spring.
5. Fog the engine if required. Fogging oil coats the inside of the cylinders against corrosion. Many fuel-injected motors have their own storage procedure, so check the manual before spraying anything into the intake.
6. Grease and inspect. Grease the fittings, check the propeller and shaft for fishing line, and inspect the anodes. Replace anodes that are heavily worn.
7. Store it properly. Keep the motor upright or tilted down so water drains from the gearcase and cooling passages. Charge and disconnect the battery on electric-start models, and cover the motor.

Year-round outboard maintenance checklist

• After every trip: on water-cooled models, flush as the manual directs, especially after saltwater use, and check the telltale (cooling water indicator) stream on the next start.
• Every season or at the manual’s interval: change the engine oil and filter, change the gear oil, and inspect the fuel filter, spark plugs and water pump impeller where fitted.
• Regularly: check the propeller for damage, the anodes for wear, and the fuel lines and primer bulb for cracks.
• New motors: follow the manufacturer’s break-in procedure, which usually limits sustained full throttle for the first hours of running.

Each of these tasks is explained step by step in our outboard motor maintenance checklist.

Electric outboards

Electric outboards such as the Torqeedo Travel have no oil, fuel or cooling water to deal with. Rinse the motor after use, keep the battery stored at the charge level the manufacturer recommends, and store it somewhere dry and above freezing.

Frequently asked questions

Do I need to winterize a four-stroke outboard?

Yes, if it will sit unused through the winter or be exposed to freezing temperatures. Follow the model’s fuel, lubrication and storage instructions; cooling-water drainage applies to water-cooled models.

How often should I change outboard oil?

Follow your owner’s manual. Most manufacturers specify a change after a set number of running hours or at least once a season, whichever comes first.

How do I flush an outboard motor?

For water-cooled outboards, attach a flushing device (often called earmuffs) or a hose to the motor’s flush port, turn on the water, and run or rinse the engine as your manual describes, until clean water comes out.

Shopping for a new motor? See outboard motors for sale, jon boat motors and portable outboard motors, and read 2 stroke vs 4 stroke outboards.

More reading: How to break in a new engine, Gas vs diesel engines, Inboard vs outboard motors, Parts of an outboard motor.