How to Winterize a Boat Motor – Protect Your Investment for Next Season

As someone who’s lived the better part of their life on water, I’ve seen firsthand the anguish of boat owners when their prized possessions fail to roar back to life at the start of a new boating season. Let me tell you, it wasn’t a pretty sight. And for a long time, I couldn’t understand why such issues were common until I stumbled upon a game-changer – winterization. When I discovered how to winterize a boat motor, it transformed my boating life.

Since then, every time I use my boat in the chill of winter, I remember the time I spent learning this essential skill. I’ve seen how much it has saved me in repair costs and the peace of mind it brings, knowing my boat is well cared for. So, now I want to share my knowledge with you.

Why Winterize Your Boat Motor?

Winterization is crucial to ensure the longevity of your outboard motor or inboard motor. During the winter, unused engines can suffer from corrosion, rust, and other damages. Winterizing your boat and particularly the motor is the best preventive measure you can take to avoid these issues and ensure a smooth start in the next boating season.

The Impact of Winter on Boat Motors

During the cold winter months, any residual water in your motor can freeze and cause significant damage. Moreover, fuel left in the carburetor or fuel system can gum up and prevent the motor from running smoothly. The winterization process helps to address these issues.

Step Guide to Winterizing an Outboard Motor

Winterizing an outboard motor involves several steps, including treating the fuel, changing the oil, and using fogging oil. It’s essential to follow the right process for either a four-stroke outboard motor or a 2-stroke outboard motor.

How to Winterize a Four-Stroke Outboard Motor

Whether you’re working with a Mercury outboard or another brand, winterizing a four-stroke outboard motor involves similar steps.

  1. Start the Engine: Begin the winterizing process by starting the engine to warm it up. It allows the fresh oil to circulate and reach internal parts more efficiently later on.
  2. Change the Oil and Oil Filter: Replace the old engine oil and oil filter. Make sure you use fresh oil designed for your motor model. Always remember to recycle used oil responsibly.
  3. Run Antifreeze: Connect a garden hose to your motor’s water intake and run non-toxic antifreeze through the system. It will prevent any remaining water from freezing and causing damage.
  4. Use Fogging Oil: Inject fogging oil into the carburetors or the electronic fuel injection system while the motor is running. It prevents corrosion from forming on internal engine parts during winter storage.

How to De-Winterize a Boat Motor

When the new boating season arrives, you’ll need to de-winterize your boat motor. Start by checking the engine and replacing the fuel filter if needed. Follow your owner’s manual for specifics.

Frequently Asked Questions:

Why should I winterize my boat motor?

Winterizing your boat motor protects it from potential damage due to freezing temperatures and idle time.

What’s the difference between winterizing a four-stroke and a two-stroke outboard motor?

While the fundamental steps remain similar, a two-stroke outboard motor does not require an oil change as the oil is mixed with the fuel.

Do I need professional help to winterize my boat motor?

While you can seek professional help, winterizing a boat motor is a task that most boat owners can handle with the right tools and guidance.

Can I use my boat in winter without winterizing it?

If you are regularly using your boat in winter, you might not need to winterize it. However, it is still recommended to winterize your motor if your boat will be idle for a prolonged period.

What happens if I don’t winterize my boat motor?

Failure to winterize your boat motor can lead to serious issues such as engine block cracks, corrosion, and fuel system damages.


Learning how to winterize a boat motor is an investment that pays off greatly in the long run. Not only will it save you from costly repairs, but it also ensures that your boat is ready to hit the water once the new boating season starts. So, take some time this winter to give your boat the care it deserves, and you’ll be rewarded with smooth sailing come the springtime.


  • Anna Kristensen

    Anna Kristensen is an avid sailor and experienced yacht captain. With her vast experience sailing across different seas and weather conditions, she offers expert advice on navigation, seamanship, and offshore sailing. Anna's in-depth knowledge of sailing techniques, safety protocols, and voyage planning makes her an excellent resource for sailors looking to enhance their skills and embark on memorable boating adventures.

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