Winterizing marine engines should begin with checking the winterizing instructions in your owner’s manual. Follow that procedure and use the recommended fluids. If your owner’s manual doesn’t include winterizing instructions, here is a checklist to ready your marine vehicle for storage.

outboard propellor up for maintenance

Lets Get Started

Remove the propeller.

Clean it thoroughly and check for any damage. Coat the propeller and prop shaft with a protective layer of grease.

Inspect wires and electrical connections for damage.

Make any necessary repairs. Coat them with anti-corrosive spray.

Fluids & Safeguards

Change the Oil and Oil Filter

Run the engine to heat the oil. Then change the oil in both the Crankcase and Gearbox with the manufacturers recommended lubricant.

Flush with Freshwater

Use a flushing attachment if you have one or reverse flush the engine with “earmuffs”. Run the engine in idle while flushing until the water leaves clean.

Flush and Drain with 50/50 Propylene Glycol Mixture

This provides an anti-corrosive film and works as anti-freeze for any remaining water.

Drain the Cooling System

Disconnect the cooling system from the freshwater. Position the engine upright. Open any drainplugs and handcrank the engine a few times to ensure all of the water drains.

Change Coolant—Inboard

Use the manufacturer recommended 50/50 solution

Stop Fuel Degradation

Add fuel stabilizer to gas fueled vehicles according to the product’s directions. Leave a full tank to prevent water sneaking into the fuel supply. Use Biocide for diesel engines.

If you prefer to store your gasoline engine with an empty tank (there is a bit of controversy here) disconnect the fuel lines before the next step and completely empty the tank. Diesel engines should be stored with a full tank.

Drain and Fog the Carburetor—Gas Engines

With the engine idling, spray fogging oil into the throttle body throat or carburetor. Degrading fuel gums up or corrodes parts during storage, so either turn the fuel valve to off or pinch the supply line closed to burn away all the fuel in the system.

Fog the Cylinders—Gas

When the engine stops after the fuel cut-off, remove the spark plugs. Spray fogging oil into the cylinders and rotate the flywheel to circulate it. Inspect the spark plugs to see if they need regapped or replaced. Do so if necessary. Then reinstall the spark plugs.

Fog the Intake Manifold—Diesel

Spray fogging oil into the intake and hand-turn the engine over to distribute the oil.

Final touches, Packing Up

Disconnect the Battery

Store it-- fully charged-- off of the ground in a room temperature area.  Charge the battery periodically or use a smartcharger.

Clean and grease all visible metallic engine parts.

Coat unpainted engine parts with anti-corrosive spray.

Cover Up

Be sure the cover allows air circulation underneath it, but keeps out water and snow.

Now just find the patience to wait for spring.