Do you need to winterize a 4 stroke outboard motor?

Winterizing a 4 stroke outboard motor is an important part of preparing your boat for storage during the winter months. By taking the proper steps to winterize your motor, you can help prevent issues like corrosion, fuel system problems, and lower unit damage that can occur when an outboard sits idle for extended periods of time.

Should you winterize a 4 stroke outboard?

In general, it is recommended to winterize any 4 stroke outboard motor that will be out of use for more than 2 months. Here are some reasons why winterizing is important:

• Prevents fuel from going stale – Gasoline can start to degrade and form deposits after just 30 days. Stale fuel can clog carburetors and fuel injectors.
• Avoids corrosion – Water left inside the engine can lead to rust and corrosion over time. Proper winterization flushes the system.
• Protects rubber seals – Seals can dry out and crack if left exposed to air all winter. Running the engine on winterizing fluid coats the seals.
• Lubricates the cylinders – The fogging oil used in winterizing coats cylinder walls to prevent rust and wear.
• Saves the battery – Disconnecting and storing the battery properly over winter prevents parasitic loads from draining it.

So unless your motor will be used consistently year-round, it’s highly recommended to winterize your 4 stroke outboard. The small investment of time and money up front can avoid expensive repairs later on.

What you need to winterize a 4 stroke outboard

Here are the basic supplies you’ll need to winterize a 4 stroke outboard motor:

• Engine fogging oil – Special oil designed to coat internal engine parts for winter storage.
• Fuel stabilizer – Additive that treats fuel to prevent deterioration and deposits.
• Engine ear muffs – Attaches to the lower unit to supply water for flushing.
• Phillips head screwdriver – For disconnecting battery cables.
• Storage fuel – Non-ethanol gasoline for filling the tank after treating.
• Clean rags – For wiping down engine exterior and drying any residual water.
• Boat storage cover – Protects engine from snow, rain, sun, etc.

These basic supplies are fairly inexpensive and available at any marine supply store. Fogging oil, fuel stabilizer, and non-ethanol gasoline formulated specifically for boat storage are essential.

How to winterize a 4 stroke outboard motor

Here is a step-by-step guide to properly winterizing a 4 stroke outboard motor:

1. Flush the cooling system – Attach a set of engine ear muffs to the water intake and start the engine, letting it run for 10-15 minutes in neutral. This flushes any saltwater, sediment or deposits from the system.
2. Change gear lube – Drain and refill the lower unit gear lube if due for a change. Use manufacturer recommended lube for winter storage.
3. Stabilize the fuel – Fill the tank with fresh gasoline and add fuel stabilizer according to instructions. Run the engine for 10 minutes to circulate stabilized fuel through the system.
4. Fog the engine – Remove all spark plugs and spray fogging oil into each cylinder. Rotate the flywheel manually to spread oil throughout. Replace spark plugs.
5. Disconnect the battery – Unhook the battery cables from the battery terminals. Clean corrosion from terminals and coat with a battery protector spray.
6. Spray storage fuel in carbs – If equipped with a carburetor, spray storage fuel or carburetor cleaner into the air intakes while cranking the engine over. This coats internal carb components.
7. Change lower unit oil – Drain and fill the lower gear case with manufacturer recommended oil for winter storage.
8. Clean and wax – Wipe down the engine exterior with a clean rag. Apply a coat of wax to protect from moisture.
9. Store properly – Move the motor to an indoor location if possible, otherwise keep it vertical and covered from the elements.

This comprehensive winterizing process will help keep all components of your 4 stroke outboard protected while not in use.

Tips for winterizing 4 stroke outboards

• Read your owner’s manual for any winterizing instructions specific to your motor.
• Make sure to use marine-grade storage fuel with 10% ethanol or less.
• Stabilize the fuel first before adding to the tank to treat any existing fuel.
• Spray fogging oil into the carbs even if fuel injected to coat intake valves.
• Disconnect and charge the battery monthly, or better yet, take it indoors.
• If outdoors, elevate the motor to allow water drainage and cover with a vented canvas.
• Change the lower unit oil at the beginning and end of winter storage.
• Always verify the engine ear muffs provide good water pressure before flushing.
• Start the motor up periodically if storing for more than 4-5 months.

Taking extra care when winterizing your motor will pay off when it easily starts up again in spring.

Can you skip winterizing a 4 stroke outboard?

It is possible to skip winterizing an outboard motor, but doing so comes with substantial risks:

• Gasoline can oxidize and go bad within 1-2 months without treatment.
• Untreated fuel can leave gum, varnish, and carbon deposits on injectors and valves.
• Corrosion can rapidly damage cooling system components left filled with water.
• Rubber seals and gaskets can shrink and crack when dried out.
• Cylinders are more prone to pitting and rust without a protective coating of oil.

While you may get away with skipping winterization for a season or two, the potential for serious engine damage exponentially increases if leaving your motor untreated for an extended off-season. The small upfront investment is worthwhile insurance against costly repairs later on.

Winterizing 4 stroke outboard motors in cold climates

Additional winterizing steps may be necessary for boats stored where temperatures regularly dip below freezing:

• Use extra fogging oil in the cylinders and carbs to leave a thicker coating.
• Fill the fuel tank to reduce condensation and allow for fuel expansion as temperatures rise.
• Add fuel stabilizer rated for severely cold temperatures.
• Disconnect hoses and completely drain cooling system if storing outdoors.
• Store battery indoors rather than leaving it in the boat.
• Choose synthetic gear lube rather than standard for extreme low temps.
• Remove propeller before covering engine to prevent freeze up.

Taking extra precautions if below freezing temperatures are expected will help prevent issues with fuel gelling, cracked blocks/hoses, seized pumps, and other cold weather-related problems.

DIY winterizing vs having a dealer do it

Many boat owners are capable of properly winterizing their 4 stroke outboards themselves following the steps above. However, hiring a boat dealer to winterize your motor has some advantages:

• Dealers use commercial-grade flushing and fogging equipment for the most thorough winterization.
• Technicians are trained on winterizing procedures for all motor models.
• You avoid the hassle and mess of draining fluids and pulling spark plugs.
• Any needed repairs or gasket replacements can be identified and addressed.
• Peace of mind knowing the job was performed correctly.

That said, dealers typically charge $150-$300 or more for winterization services. For smaller portable outboards, DIY winterizing can save money if you follow the proper procedures.

Winterizing an outboard checklist

Use this winterizing checklist to keep your 4 stroke outboard protected while in seasonal storage:

Task	Completed?
Flush and drain cooling system	☐
Add fuel stabilizer to tank	☐
Run engine to circulate stabilized fuel	☐
Fog engine cylinders and carburetors	☐
Change lower unit gear lube	☐
Disconnect and store battery	☐
Clean and wax engine exterior	☐
Store engine covered and protected	☐

Conclusion

Taking the time to properly winterize your 4 stroke outboard motor is one of the most important end-of-season maintenance tasks. While the specific steps vary by model, the basics involve flushing the system, stabilizing fuel, fogging the engine, changing fluids, and disconnecting the battery. Follow the winterization procedures outlined in your owner’s manual or have a certified dealer winterize your motor. Keep your outboard protected from the elements and you’ll ensure it’s ready for reliable performance when launching again in spring.