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When the summer fishing season or recreational fun is done and the cold weather is about to set in, your boat will need to be put stored away, and the motor will need some extra care. Preparing it for the harsh winters will be necessary if you want to keep your engine going strong for many years to come. 

To winterize your outboard motor, you only need a few simple tools. Although one piece of specialized equipment you should invest in is an outboard motor flushing device. You’ll also need some fuel stabilizer and a can of fogging oil. West Marine walks you through how to winterize your motor and why it’s important.

Stabilize the fuel in the outboard motor

One of the most important steps to getting your motor ready for winter is to stabilize the fuel in the tank, no matter if you have a Mercury brand motor or one of the many others. Gasoline left to sit for months will separate, releasing the water from the fuel. The moisture will start corroding the internal parts, which could be costly to fix. Especially if you try to run the motor with the water inside. 

Drain any old gasoline from the tank and fill with a fresh batch until it’s approximately 95% full. You want to make sure to leave a little room for the fuel to expand when temperatures change drastically. Add a fuel stabilizer to the gas. This will help the fuel from breaking down. While you’re at it, replace the fuel filter, if your tank has one.

Next, you’ll need to run the motor for about 15 minutes or so. You’ll want to do this so that the fuel gets into the fuel lines, and other internal parts so they can get coated with the fuel/stabilizer mixture. Failure to do this will cause damage to your motor when you try to run it in the spring. If you choose, you can also just drain the old fuel from the tank and store it empty over the winter. 

Flush and drain water from your motor

Two boats tied up a dock
Boats securely tied to a dock | Evan Richman/Globe Staff

Another important factor when winterizing your outboard motor is to flush it with water. This will help get rid of any sediment collecting within the system. Hook up a garden hose to a motor flush attachment, which will cover the water intake on the lower unit of the motor. Turn on the water and then start the motor.

Once you’ve completed flushing it, then you need to make sure you’ve drained any water from the system. Move the motor back and forth to help get all the water out. If you leave moisture in the motor and it freezes, you could crack it, which would cost you quite a bit to repair or possibly replace the motor next season.

Some experts recommend that you use antifreeze instead of water. If you choose to do that, make sure you’re using an antifreeze made special for marine applications. The antifreeze will not freeze up inside the motor over the winter. 

Protect the internal parts of the outboard motor when you winterize it

When you’re almost done flushing out the motor, use your can of fogging oil and spray the oil directly into the air intakes of your carburetor. You’ll notice the motor starts to choke and sputter. You’ll also see white smoke coming from the engine, this is normal.

Disconnect the fuel line from the outboard motor and keep spraying the fogging oil into the air intakes. You can also remove the spark plugs and spray the fogging oil into each one of the plug’s chambers. Eventually, the motor will stall. 

It’s important to note that if you have an EFI engine, like some of the newer Honda motors have, you should not do the fogging oil step as you’ll damage it. Instead, use 2-cycle engine oil in the fuel/water separator. This will coat the internal parts and get it ready for winter. 

Now is also a good time to replace the spark plugs and drain plugs. Then put the motor’s cover back on. You can store your engine on the back of the boat, making sure it sits straight up and down, to allow for more water to drain out. Or you can remove it and store it in a warm area. 

Taking steps to prevent damage to your motor while it sits over the winter season, will help the engine last a long time. It takes just a few different steps, but if you’re not comfortable doing it yourself, let a professional winterize it for you. 


Every Boater Should Have This Simple Device Installed