Changing Engine Oil When Storing a Boat

Oil protects every vital internal component of an outboard engine, ensuring its health and longevity.

Outboard engine interior

A boat motor is subject to much more rigorous conditions than a traditional car’s engine. While a car motor spends a lot of time cruising or coasting, a boat’s engine is constantly under a heavy load and running at high RPM. Because of these additional strains, it’s essential to change a boat engine’s oil on a regular basis. And it’s especially important to change the oil when preparing a boat for storage (commonly known as “winterizing”, regardless of the season).

Why Change the Engine Oil for Storage

Whether you’re storing your boat for winter or during hurricane season, its engine lubricants should always be changed.

Outboard engine oil change

Engine oil protects the motor even when it’s idle. Oil provides a protective barrier between the metal surfaces within the engine, and also protects against any water that may get in. Even a small amount of water in a crankcase or a gearcase will corrode the internal surface and components, particularly during extended periods of inactivity.

Unscheduled Oil Change

If you’re going to store your boat for an extended period of time but the engine isn’t yet due for an oil change, it is now!  

Used dirty marine engine oil

Oil that hasn’t quite reached its change-by date will still be full of contaminants. Those include combustion gasses, carbon deposits and microscopic metal fragments suspended within the oil that cause acids to form. Contaminants in the engine oil slowly break it down and corrode the motor’s interior. By replacing the oil before you store your boat and/or outboard motor — even if it’s relatively new oil — you’ll be removing these harmful contaminants to protect your motor during its storage period.

What Else Besides Changing the Oil?

As well as changing the engine oil, fogging oil should also be used to winterize an outboard motor

Fogging is the process of ensuring all the internal components of an engine, such as seals and bearings, are coated in a protective lubricant. The fogging oil is sprayed into the carburetors or injection system while the engine is running, which causes it to cloud within the engine and coat all the surfaces.

Once again, because outboard motors have little protection from the water under normal operating conditions, they’re more likely to have traces of water within the engine itself. Fogging while winterizing an outboard motor provides additional protection and minimizes the risk of internal corrosion.

What Oil Should Be Used for Storage

The engine oil used to store an outboard motor should be the same one used for regular oil changes. 

Boat outboard engine storage

Whether you use OEM motor oil made by your outboard’s engine manufacturer or another high quality aftermarket oil, keep in mind that marine engine oil and automobile engine oil are not the same. Never cut corners by using any engine oil other than what’s recommended by your boat engine’s manufacturer.

  • Oils with an API rating that begins with a letter ‘S’ are only for use with gasoline powered motors
  • Oils with an API rating beginning with ‘C’ are only for use with diesel powered engines

Don’t forget to change the oil filter as well as the oil itself before you put your boat away in storage.

Boat storage engine oil change tips

Give your boat’s engine the care it deserves both in and out of the water. Whenever you’re ready to take your boat and its outboard out of storage, watch the video below to learn how to dewinterize an outboard motor

Outboard de-winterization maintenance



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