When the temperature falls below freezing, if there is water inside your engine or gear case, the result can be a cracked block or housing and a repair bill that runs into the thousands. It is easy enough to prevent this unhappy circumstance by putting your boat's engine to bed properly at the end of the boating season.

Winterize Your Outboard Engine

 Freshwater flush

Use a flushing attachment or run the outboard in a tank filled with clean water.

Empty fuel lines and carburetors

While the engine is still running, disconnect the fuel line from the engine. When the engine dies, the fuel delivery components will be empty, preventing gums from forming in the stagnant gasoline and clogging lines and jets or injectors.

Fog the carburetor intake(s)

Before the engine runs out of fuel, spray fogging oil into the carburetor(s). Fogging oil is an anticorrosive that will protect the internal surfaces of the carburetor and the cylinders. Typically the engine will run rough just before it runs out of fuel. As that happens, give the carburetor(s) a heavier shot of fogging oil to make sure internal surfaces are fully coated.

Drain cooling passages

Disconnect the flush attachment or remove the motor from the flush tank. With the motor upright, let all water drain out of the pick-up. Open drain plugs (if any--see your owner's manual) to empty the powerhead and intermediate housing. Crank the motor a couple of times by hand or "bump" it with the starter to empty the water pump. If the motor will be exposed to free

Remove the spark plugs and spray fogging oil into the holes to coat the interior surfaces of the cylinders. Rotate the flywheel a few turns to spread the oil on the cylinder walls. While the plugs are out is the time to check them and regap or replace as required. Reinstall the spark plugs.

Lubricate linkages and the electric starter drive mechanism

Clean all pivots and visible gears and protect them for the winter with oil or grease, as specified in your owner's manual.

Drain and refill gearcase

Use lubricant specified in your owner's manual. Fill oil tank. This will prevent condensation from forming inside the tank.

Touch up damaged paint

Mist-coat powerhead with an anticorrosion spray.

Drain fuel tank and supply lines

Starting your engine in the spring with old gasoline is an invitation to problems. Manage the last few weeks of your boating season to leave your fuel tank(s) close to empty, then drain the fuel that remains. Use it in your snow blower or burn it in your car, but leave gasoline tanks and lines empty.

 If emptying the tank completely is not practical for your boat, then top it off to 95% full. This is particularly important since the introduction of alcohol into the gasoline supply. Gasoline with ethanol is subject to phase separation if water gets into the fuel, which it will surely do with a half-empty tank over the winter. Filling the tank limits the air space inside the tank and reduces the potential for internal condensation.

Stabilize the fuel

If you leave your tank full, dose it with an appropriate amount of gasoline stabilizer to combat the formation of passage-clogging gums.

Clean and liberally lubricate propeller shaft

The off season is the perfect time to have your prop(s) serviced. If the engine will be stored on the boat, take the prop(s) home to discourage theft.

Store upright

Laying the engine down risks water draining where it shouldn't. An engine stand is easy enough to cobble together.