How to Winterize Outboard Motors

How to Winterize Outboard Motors

If you live in a climate that prevents you from using outboard motors year-round, it’s important to winterize so your motors will be ready to perform for you during the next boating season.

Safety First

Winterizing outboard motors can expose you to some hazardous substances. Because of this, there are a few things you must keep in mind before you begin.

  • NEVER run outboard motors in a garage or other enclosed space. (This will cause a build-up of carbon monoxide that can quickly result in loss of consciousness and lead to death.)

  • ALWAYS stop the engine and allow it to cool before handling fuel. Gasoline is extremely flammable and combustible. Keep fuel away from heat, sparks or flame.
  • ALWAYS properly dispose of any unused gasoline, engine oil, or gear oil according to the laws and regulations in your area.

What You’ll Need

  • An aerosol can of fogging oil
  • Fuel stabilizer
  • Spark-plug gapping tool or new spark plugs if needed
  • Garden hose
  • Flushing attachments (Earmuffs) or large barrel filled with clean water
  • If storing away from your boat, an engine stand for vertical storage

Always Consult Your Owner’s Manual

Because instructions for winterizing outboard motors will vary by manufacturer, type, and size of motor, be sure to consult your owner’s manual for detailed instructions regarding your specific make and model.

Some General Guidelines

Flush Your Outboard with Fresh Water

Start by flushing your outboard with fresh water. For this, you’ll need specially designed “earmuffs” to place over your motor’s raw-water intake ports. You’ll also need a garden hose.

Or, you can flush your motor in a barrel or clean trash can that’s deep enough so that water will cover the intakes. If using the submersion method, you may also want to add a salt remover to the water.

Important: After flushing, make absolutely sure that no water remains in your engine prior to storage. (Trapped water will expand in freezing temperatures and will damage your engine.)

Drain or Winterize Your Outboard’s Fuel

Years ago, you could place an engine with gasoline in it in long-term storage without any issues. That’s because traditional petroleum-based fuels did not contain ethanol or biofuels. Today’s gasoline is mixed with ethanol. Fuels containing ethanol will oxidize, darken and stratify during storage of more than two months, causing them to become “sticky” and to “gum up” your engine. This will result in problems and potentially costly damage when you attempt to use your motor again next season. Because of this, you can’t just leave a half-tank of gas to sit there in your outboard, unused until spring.

There are two ways to address this issue. You can either drain the gas tank and carburetor into a gasoline-safe container and use the fuel for another purpose (to run your chainsaw, for example), or you can fill the rest of your tank with a storage additive that contains an anti-ethanol stabilizer.

If you do drain your engine, there will still be a small amount of fuel left in your carburetor that you’ll want to use up by running the engine. (See “Fogging” Your Outboard’s Engine, below.)    

Change the Outboard’s Engine and Gear Oil

Prior to long-term storage, you also should change the engine oil (and, if present, the oil filter). This will prevent any contaminants from corroding your engine.

This is also a good time to change your engine’s gear oil. This will prevent contaminants or trapped water from damaging the gear case.

“Fogging” Your Outboard’s Engine

To help avoid corrosion, you’ll also want to “fog” your outboard’s engine.

After you’ve drained your fuel, there will still be a small amount of fuel remaining in the carburetor. Turn on the engine, and just before the motor runs out of fuel (you’ll know this is imminent when you hear the engine become rougher), take your aerosol can of fogging oil and spray it into your carburetor. This will help protect the cylinders and other internal surfaces from corroding.

Finally, with your engine OFF – and after it has cooled – remove your spark plugs and spray fogging oil into the holes. Next, “bump” the starter to distribute the fogging oil onto the cylinder walls. Afterward, re-gap your spark plugs and reinsert them or replace them as needed.

Properly Store Outboard Motors

If you’ve chosen to completely drain the engine oil and fuel from your motor, you have the option of storing it horizontally, with the tiller handle facing upward. If you choose this option, make sure that the stored motor rests on its case protectors.

Otherwise, store your outboard vertically. Use an engine stand built specifically for your outboard motor to store in an upright position.

If you wish to provide a dust cover for your outboard during long-term storage, make sure the material is breathable. (Do not use plastic, as it will trap moisture that can cause rust and corrosion of your engine.)

Remember to consult your owner’s manual and dealer for specific guidelines that may or may not be applicable depending on your specific model(s).

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