how to winterize an outboard motor

How to Winterize an Outboard Motor


As the colder months approach, it’s crucial for boat owners to prepare their vessels for winter storage. One of the most critical aspects of this process is winterizing the outboard motor. Proper winterization ensures that your motor is protected from the harsh elements, preventing damage and extending its lifespan. In this guide, we’ll walk you through the step-by-step process of how to winterize an outboard motor to keep it in top condition for the next boating season.

1. Gathering the Necessary Supplies

Before you start the winterization process, it’s essential to gather all the necessary supplies. This includes engine oil, fuel stabilizer, fogging oil, a fuel filter, a lower unit gear oil pump, a flush kit, and a set of basic hand tools. Having everything ready will make the process smoother and more efficient.

2. Changing the Engine Oil

Begin by changing the engine oil. Used oil contains contaminants that can lead to corrosion during the winter months. Remove the drain plug and allow the old oil to drain completely. Replace the oil filter and refill the engine with the manufacturer-recommended oil. This ensures that your engine will start smoothly when you’re ready to hit the water again.

3. Stabilizing the Fuel System

Fuel can degrade over time, leading to carburetor clogs and other engine issues. Adding a fuel stabilizer to the tank helps prevent fuel breakdown during the winter months. Run the engine for a few minutes to ensure that the stabilized fuel reaches the carburetor and fuel injectors. This simple step goes a long way in preserving the integrity of your outboard motor.

4. Flushing the Cooling System

Flush the cooling system with fresh water to remove any salt, debris, or other contaminants. This is especially important for those who use their boats in saltwater environments. Connect a garden hose to a flush kit and let water run through the cooling system while the engine is running. Flushing the system helps prevent corrosion and ensures that your outboard motor is ready for the next season.

5. Fogging the Engine

Fogging the engine is a critical step in protecting internal components from rust and corrosion. Remove the spark plug wires and spray fogging oil into each cylinder while turning the engine over. This coats the internal surfaces with a protective layer that safeguards against moisture and oxidation. Reconnect the spark plug wires once the fogging process is complete.

6. Inspecting and Changing the Fuel Filter

Inspect the fuel filter for any signs of dirt or water. If it’s a replaceable filter, consider changing it to ensure that your engine receives clean fuel. A clean fuel system reduces the risk of clogs and improves overall engine performance. This small investment in maintenance can save you from more significant issues down the line.

7. Checking and Topping off Lower Unit Gear Oil

Inspect the lower unit gear oil for any signs of water intrusion or contamination. Milky or discolored oil indicates water entry, which can lead to gear corrosion. Use a lower unit gear oil pump to add fresh gear oil, ensuring that the lower unit is filled to the recommended level. This step is crucial in preventing corrosion and maintaining smooth gear operation.

8. Removing the Battery

Cold temperatures can be harsh on batteries, leading to reduced performance and potential damage. Remove the boat’s battery and store it in a cool, dry place. Consider using a battery maintainer to keep it charged throughout the winter. This not only preserves the battery life but also ensures that your boat is ready to go when the warmer months return.

9. Cleaning and Waxing

Before covering your boat for the winter, give it a thorough cleaning. Remove any dirt, grime, or salt deposits to prevent corrosion. Apply a coat of wax to protect the boat’s exterior from the elements. Cleaning and waxing not only preserve the aesthetics but also contribute to the overall longevity of your watercraft.


Winterizing your outboard motor is a crucial aspect of boat maintenance that shouldn’t be overlooked. By following these steps, you can protect your investment and ensure that your outboard motor is ready for action when the boating season returns. Taking the time to properly winterize your motor can save you from costly repairs and extend the life of your boat, allowing you to enjoy many more seasons on the water.

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