How to winterize your outboard

Graciously submitted by Pete Burns. Thanks Peter!!

To help keep your engine in tip-top condition for years to come, it is important that you “winterize” your outboard for off-season storage. By winterizing your outboard, you will help ensure that your outboard will be ready to go at the start of next year's boating season. Although you can winterize your outboard yourself, most dealers will perform this service for you at a very reasonable rate.

Step 1: Thoroughly flush your engine with clean, fresh water and let the water completely drain from the engine. Wash any dirt, grease, etc. from the exterior of the engine.

Caution: To avoid injury in the event of accidental starting, be sure and remove the prop and the stop switch lanyard cord from your outboard before proceeding.

If the outboard is water cooled; running your outboard without an adequate source of cooling water will result in severe damage to your outboard!

Smaller Horsepower Outboard (2.5 & 3.5 hp)
smaller outboards, the simplest way to flush your outboard is by using a large bucket of water. Be sure the bucket is large enough to completely cover the water intake ports on the lower unit of the outboard. Also be sure that the bucket is wide enough so that no part of the motor will touch the sides/bottom of the bucket. Securely mount your outboard on a sawhorse or some other type of apparatus that will allow safe operation of your outboard.

5 hp and up:
The 5 - 140 hp comes equipped with a “flushing plug” which can be attached to a hose for flushing the engine with fresh water or purchase a set of “ear muffs” (available at your local marine dealer). This equipment attaches to your garden hose and clamps on to your outboard's lower unit, covering the water intake ports. Turn the garden hose on full before starting your engine. (Note: "ear muffs" will not work on some smaller 5 hp. With a 5 hp you will need to either use the flushing plug or use the “bucket technique” as described above).

Run your outboard at normal idle speed for 5-10 minutes to allow the engine to warm up and to ensure your outboard is thoroughly flushed with clean water.

After flushing the outboard, allow the water to completely drain from the engine (see Step 2 before you shut off your engine). Your outboard should be in a vertical position for the water to completely drain. While you're waiting for your engine to drain, wipe off any dirt, grease, etc. from the exterior of the engine.

Step 2: Drain all fuel from the fuel hoses, fuel pump and carburetor.

When you have completed the fresh water flush in Step 1, disconnect the fuel line at the motor and continue running the motor until it runs out of gas. It is extremely important to ensure that all of the fuel has been drained from the carburetor otherwise any fuel/oil mixture remaining will evaporate and leave deposits (also called varnish, gum, etc). in the carburetor.

To drain the fuel from the carburetor you can use one of these techniques:

As the fuel begins to run out and the motor starts to "die", choke the engine a little until the RPM's pick back up. Continue choking the engine as the engine starts to die out until the fuel supply is finally exhausted.

Remove the drain screw from the carburetor bowl and allow all fuel to drain out. Replace the screw when finished. Although this technique requires a bit more effort than the first, it is recommended to use this procedure to fully ensure that all fuel has been removed from the carburetor.
If you have fuel left in your tank you may want to add some fuel stabilizer to it, so that it can be used the following season. Fuel stabilizer will also help prevent condensation from forming in your fuel tank.

If your outboard is not an oil-injected model (i.e. you mix your gas/oil manually), I highly recommend you do not store the petrol for extended periods of time. Over time, the petrol and oil will separate which will lead to a lack of lubrication to your engine.

Step 3: Treat your outboard with “storage oil” (also called “fogging oil”).

Storage oil comes in an aerosol spray can and is used to prevent rust on the engine's cylinder, crankshaft, bearings, pistons, etc. and can be purchased at most local marine dealers. Follow the oil manufacturer's recommendation on the amount of storage oil to use (generally about 2 ounces for each cylinder).

First, remove the spark plug(s) and the stop switch lanyard cord from your outboard. It is also a good idea to disconnect the spark plug wires from the spark plugs to prevent accidental starting.

Manual Start Outboards: Slowly turn the engine over a few times using the pull cord while spraying the storage oil into the spark plug holes.

Electric Start Outboards: Be sure you have water hooked up to your water intakes before turning over your outboard to prevent damage to your water pump. While spraying the storage oil into the spark plug holes, turn the engine over in 5 second bursts using your electric starter. Do not over “crank” your engine or you could damage the electric starter.

Step 4: Apply water resistant grease to propeller shaft. Using a wheel bearing grease (or something similar), thoroughly grease the prop shaft and prop shaft threads.

Step 5: Change the gear oil in the lower unit (see Tech Talk tips for complete step-by-step instructions).

Step 6: Apply water resistant grease to all moving parts, joints, bolts, nuts, and plastic fittings.

Step 7: To help keep your factory finish looking new, apply a light coat of oil to the exterior. Or you can also wax the exterior of your outboard using a high grade automobile wax.

Step 8: Store the engine vertically in a dry area.

If you store your boat in the water there are several schools of thoughts regarding whether you should store your engine in or out of the water. There are advantages and disadvantages of both ways and unfortunately there is no one “correct” or “best” way. Numerous factors such as temperature, salt/fresh water, algae growth, corrosion, etc. must be taken into account when deciding whether to leave your outboard in the water or tilt it up out of the water.

To find out which is “best” way I recommend you ask your local marina, fellow boaters in your area, etc. how they store their boat/outboard during the off-season.

Factors to keep in mind:

Storing in water allows algae and corrosion to affect your outboard.
Storing out of the water could cause damage if the outside temperature reaches freezing and there is water in your lower unit.
If you store your motor tilted up, I recommend you remove your prop to decrease the temptation of someone stealing your prop.
Storing down in the salt water drastically increases the potential for corrosion.
Battery Storage

Step 1: Disconnect the battery cables and clean the battery terminals using a wire brush.

Step 2: Recharge the battery to full strength. You should also recharge the battery once a month during the off-season to prevent electrical discharge and degradation of the electrolytes.

Step 3: Clean the exterior of the battery.

Step 4: Apply grease (Vaseline works nicely) to the battery terminals.

Step 5: Store your battery in a dry place.

I found this info and felt it may be useful to readers who have little or no knowledge of the importance of winterizing an outboard. I guess there is a lot of other experience out there that could be shared regarding this.


(These are recommendations. CGOA makes no warranty on these procedures. Make your own final decisions as how to winterize your boat's motor)