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Outboard motor end of season maintenance

by Boat Accessories Australia 1 May 2019 22:22 UTC
Motors © Boat Accessories Australia

As another summer draws to a close, some boat owners decide to pack away their boat for six months. But not all boat owners are sure what preparation they should do on a boat motor that will sit idle for several months.

The time and effort spent winterising your boat motor can save you money when it comes time to put it back in the water.

Flush out the motor

While it's important to flush out the motor after every boat trip, it's even more important after the final trip of the season. Whether the boat has been in the river or ocean, the motor still needs flushing with tap water.

Attach a hose to the mounts on the motor and turn on the hose. The water pump will flush out the system. Use a screw in outboard motor flusher for Mercury, Mariner, Honda, some Tohatsu and Suzuki motors. For Tohatsu 8-9.8hp motors, use this outboard engine flusher.

If you have an older style motor, use a set of universal outboard motor flushers. The muffs fit a standard garden hose connection and are available in a range of sizes to best suit your outboard motor.

Check the water pump

While the motor is running, check the temperature of the water exiting the motor. The water should be warm but not hot. If the water is hot and the flow isn't good, shut down the engine followed by the water supply. Take off the outflow tube and see if there are any particles in there obstructing the flow. Blow into the tube or use a piece of wire to dislodge any particles. Try turning the engine on again and if the flow hasn't improved, switch off the motor and see a mechanic about checking on the water pump impeller.

Turn off the engine

It is important to make sure you always run your outboard motor with a water supply to the lower part of the motor. If you run your motor dry, it can take only seconds for the water pump impeller to become damaged.

Disconnect the fuel line

Once you have finished flushing the motor, it's important to disconnect the motor from the fuel source if you are not using it for a while. Any old fuel in an engine can gum it up and cause problems so make sure to burn off any fuel in the carburettor while taking care to not overheat the engine.

Under the cowling

Safety Tip: Switch off the engine and disconnected the battery before removing the cowling.

Check for water in the engine compartment. If there is any water or other liquids, consult a boat mechanic. Next, wipe down the engine components with a rag to remove any foreign particles. Take a can of Inox Lubricant or Industry Grade Lanolin Spray and spray all moving parts including the pivots, shift mechanism, throttle cables and carburettor valves. Make sure they are lubricated and greased so they can still move in a few months' time.

Before replacing the cowling back on the motor, give it a good wipe over with a clean cloth inside and out then lock it in place so the motor stays dry and free of spiders.

Fuel tanks

If your boat is going to be left unsecured, it may be best to remove your fuel tanks to avoid any possible theft. You can leave the fuel in the tanks to stop condensation but remember to discard it in spring and replace with fresh fuel. You can also use a fuel additive like Sta-Bil Fuel Stabiliser to prevent build-up of gum or varnish during the fuel storage. For something a little stronger, use the Sta-Bil Marine Fuel Stabiliser which is designed specifically for the marine environment and preventing ethanol fuel related damage or corrosion caused by ethanol and moisture induced water attraction.


Wipe over the battery points to clean off any dirt or water. If you are storing the fuel tanks in your garage, it might be worth moving your battery inside as well.

Cover up

One of the best things you can do for your motor over winter is to keep it covered. Invest in a cover or use a small tarp taped or roped in place. If you leave your boat out near the verge, it is vulnerable to having the motor stolen, so use an outboard motor lock. The stainless steel motor lock fits over the thumb screws of the motor attachment clamps so they can't be undone.

If you prefer to remove your motor and store it off the boat, ask a friend to help unscrew it from the bracket or use an outboard motor trolley. Check the motor bracket is in good condition and wipe over to stop corrosion.

With a little extra time and effort spent on winterising your boat motor now, you can be confident your motor will be in good working condition when the weather warms up again. Now you're ready to wait out winter in front of the footy.

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