How to remove corrosion from outboard motors

Updated November 21, 2016

Many small watercraft are propelled by outboard motors. These motors are self-contained units that include an engine, gearbox and propeller, designed to be attached to the outside of the vehicle. Outboard motors, especially those utilised in salt water, are subject to corrosion. As water creeps into joints and parts, the motor becomes damaged. Treating and removing corrosion is a fairly simple process, if it's caught in the early stages.

Gather your corrosion remover, protective eye wear and gloves. Work in a well ventilated but confined area to limit any contamination caused by the rust removing products.

Check the motor for surface and interior corrosion. Corroded areas often are found near chipped or scratched paint. Look for a powdery, reddish brown material on the metallic surfaces of the engine. Some corrosion appears as pock marks of brown or red. If necessary, remove pistons and other essential parts to treat the corrosion. Apply the remover according to the manufacturer's recommendations. Some manufacturers require the use of water to rinse the remover away.

Rinse the motor and allow it to dry thoroughly. Once the rust removing product has been cleaned, rinse the motor well to ensure the chemicals have been removed from all the parts. Do not reinstall any interior parts of the motor until they have dried completely.

Prepare your work area. Gather your safety supplies, along with vinegar, lemon, washing soda, water and the battery charger. Have paper towels or rags available. Work in a well ventilated location.

Apply a mixture of two parts vinegar and one part lemon juice to paper towels until they are saturated. Rest the saturated paper towels against the affected areas. Check back every 10 minutes or so, rubbing the corroded areas to see if the corrosion has been sufficiently softened for removal. The corrosion should buff away with moderate effort.

Apply 1 tbsp salt to half a lemon. Using the lemon as a scrubber, buff the corroded areas until the corrosion loosens and can be rinsed away.

Make a bath of one part washing soda to 10 parts water. This treatment works best on extensive areas of corrosion, and especially stubborn corrosion spots. Submerge the motor into the bath. Plug in a low voltage battery charger, such as one used for a riding lawnmower, and set it to its lowest capacity. Place the connector into the water for 10 second increments, until the corrosion flakes away.

Rinse your motor with fresh water after every use and when putting the boat and motor away in storage. This will help remove any salt deposits. Check your motor for any cracks or damaged parts that may allow water to seep in and create further damage.

Apply liberal amounts of corrosion inhibitor and protective grease. This step is best performed just before use on the water and before storage, and will help protect the parts from damage and water seepage.

Apply fresh paint to a corrosion-free motor to help protect it from further corrosion. Use a product marketed specifically for outboard motors.

Check your drain plug, which keeps water from entering the engine compartment.

Apply fogging oil to your carburettor during periods of non-use. This will sustain the life of your outboard motor, and help protect the sensitive interior parts from corrosive damage.


Always use protective gear when using chemicals. Exercise caution when working with moving parts and electricity.

Things You'll Need

  • Protective gloves
  • Protective eye wear
  • Chemical corrosion solution
  • Vinegar
  • Lemon juice
  • Washing soda
  • Water
  • Paper towels
  • Battery charger
  • Corrosion inhibitor
  • Outboard motor paint
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