Winterizing Your 2-Cycle Boat Engine: Step-By-Step Guide

Winterizing a 2-cycle boat engine is essential to protect it from damage during the colder months and ensure it's ready for the next boating season. The process involves several steps, including flushing the engine, changing the oil and oil filter, and treating the fuel system with a stabilizer to prevent fuel breakdown and oxidation. It's also important to fog the engine with oil to protect internal components from corrosion and rust. Additionally, greasing fittings and applying a corrosion barrier are crucial steps in the winterization process. By following these steps, boat owners can maximize the lifespan of their 2-cycle engines and avoid costly repairs caused by freezing temperatures and corrosion.

Flush the engine with fresh water

Flushing your boat engine with freshwater is a crucial step in maintaining your engine, especially after exposure to saltwater. Saltwater can cause serious damage to your engine if left inside for long periods of time. When saltwater is trapped inside an engine, it becomes oxygen-deprived and turns acidic. This acidic water is highly corrosive and can cause significant issues with your engine's components, such as clogging and corrosion.

Flushing your engine with freshwater helps to prevent these issues by removing salt residue and scale buildup, ensuring that vital cooling water can flow through your engine without obstruction. It is recommended to flush your engine after every use in saltwater and also in brackish or silty water.

• Connect a hose to the freshwater inlet valve on the top of the sea strainer. Ensure the hose valve is closed.
• Turn on the freshwater supply and check the hose for any leaks or kinks. It is important to ensure a good water flow during the flush.
• Start the engine and check for normal cooling water flow out of the exhaust port.
• Open the small freshwater inlet valve, allowing freshwater to mix with seawater.
• Close the seawater intake through the hull valve. At this point, only freshwater is being introduced into the engine.
• Recheck the water flow out of the exhaust port to ensure normal flow.
• Run the engine in neutral at idle for approximately five minutes. This allows enough time to purge seawater and replace it with freshwater.
• Shut down the engine and close the small freshwater inlet valve. It is helpful to have another person assisting to turn off the engine while you turn off the freshwater supply.
• Turn off the freshwater supply and disconnect the hose.
• Screw on the hose adapter cap onto the sea strainer.
• Leave the intake through the hull valve closed and place a reminder note on the engine start panel to open the valve before the next engine start.

By following these steps, you can effectively flush your 2-cycle boat engine with freshwater, helping to prevent corrosion and maintain the performance of your engine.

Use a marine-grade gas stabiliser

To prepare your 2-cycle boat engine for winter, it is important to use a marine-grade gas stabiliser. This will keep the fuel mix from going bad during the colder months. Marine fuel stabilisers are designed to prevent varnish, gum, and corrosion in fuel lines and engines, which can cause engine damage.

Marine-grade gas stabilisers are essential, especially if your fuel contains ethanol. This is because ethanol loves to mix with water, and if you get more than 500 parts per million of water in the fuel, it will bond with the ethanol and sink to the bottom of your tank. This is called phase separation, and it will take the octane with it, causing catastrophic engine damage.

To prevent this, you should use a marine-grade gas stabiliser in your 2-cycle boat engine. STA-BIL Marine Fuel Stabiliser is a popular option, and it is designed to be used in harsh, humid environments. It contains a higher concentration of anti-corrosion and rust inhibitors and cleaners, making it perfect for marine engines. Another option is Quicksilver Quickstor, which prevents regular and ethanol-blended fuel from oxidising and protects fuel injectors and carburetors from gum and varnish buildup.

To use a marine-grade gas stabiliser, simply pour it directly into your fuel tank before filling up with fuel. The recommended dosage is 1 ounce of stabiliser for every 10 gallons of fuel. Run the engine for about 5 minutes to treat the entire fuel system.

Drain and change the lower unit oil

To drain and change the lower unit oil, start by placing an oil pan beneath the motor. Ensure your outboard is in a vertical and upright position. The lower drain/fill plug screw is usually located on the starboard side of the lower unit, beneath the bullet-shaped portion of the lower unit housing. Adjust the trim/tilt of your outboard motor so that this plug is in the lowest position possible to drain the oil thoroughly.

Use a large screwdriver to remove the lower drain plug screw. This can be difficult due to galvanic corrosion, so try soaking the plug with penetrating oil and letting it sit overnight. You can also use a manual impact screwdriver or apply heat from a heat gun. Be careful not to strip the slot in the plug head. With the drain plug screw loosened and your catch pan in place, keep pressure on the screw so it doesn't fall into the oil. Once the oil starts to drip out, remove the screw.

Next, remove the upper vent plug screw, usually located above the cavitation plate on the starboard side of the lower unit. The oil will now drain rapidly, so give it plenty of time to drain completely—at least an hour. Inspect the oil for any signs of water contamination or gear failure, such as milky white, creamy, or grey oil. If you notice any of these issues, consult a mechanic before taking the boat back out on the water.

Now it's time to refill the lower unit with new gear oil. Attach a pump handle to a quart of marine-grade gear oil and thread the other end of the pump into the lower drain port. Pump the new oil into the lower end until it comes out of the upper drain port. Reinstall the drain screws, first screwing in the upper drain screw to prevent oil loss. Quickly remove the pump and screw in the lower drain screw—it's okay to lose a little oil.

Finally, wipe down the exterior of the lower unit to keep the oil out of the environment, and take the used oil to a recycling center.

Spray fogging oil into the cylinders

Fogging oil is an essential step in winterizing your 2-cycle boat engine. It is a form of lubrication that will protect your engine from corrosion during the winter months.

To spray fogging oil into the cylinders, start by removing the spark plugs. This will give you access to the cylinders. Once the spark plugs are removed, spray the fogging oil directly into each cylinder. Ensure that you spray the fogging oil for 4-5 seconds in each cylinder to provide a thorough coating.

After spraying the fogging oil, gently pull the starter cord to rotate the engine a couple of times. This action will spread the fogging oil across the entire inside of the cylinders, ensuring that all metal surfaces are protected.

Finally, install new spark plugs. It is important to torque the new spark plugs to the manufacturer's specifications. This will ensure a proper seal and help prevent corrosion.

By following these steps and spraying fogging oil into the cylinders, you can effectively protect your 2-cycle boat engine from corrosion during the winter season.

Disconnect the battery

Disconnecting the battery is an important step in winterizing a 2-cycle boat engine. It is recommended to disconnect the battery if your boat is stored on land, but not if it is stored in the water. This is because, in the water, you will want to ensure the bilge pumps have power in case the water level rises inside the bilge.

If you are storing your boat on land, you should disconnect the battery and store it inside in a cool, dry place, like a basement or workshop. Marine batteries should never be left outside in the cold for too long, as they can freeze. This will cause the liquid inside to freeze and the electrical connections to break, bending the plates and lowering the battery's output.

• Start by removing the negative (black) cable. You may need a wrench or a set of pliers to loosen the nut. With your hand, twist and carefully pull up on the cable near the end and slowly slide it off the terminal.
• If the cable doesn’t move, do not use a screwdriver to pry it off as this could cause damage. Instead, use a battery terminal puller.
• Once you’ve removed the cable, tuck it off to the side and out of the way.
• Next, loosen and remove the positive (red) cable from the battery. Again, be careful while pulling it off, then tuck it out of the way.

Before storing your battery, there are a few things to keep in mind:

• Check the battery for any signs of damage, such as cracks or corrosion.
• Clean the battery with a clean cloth to remove any dirt.
• Use a mixture of baking soda and water to clean the negative and positive terminals.
• Check the battery's fluid level and add distilled water if needed.
• Ensure the battery is fully charged.
• If you have a wet-cell battery, pop the cap on the top of the battery case and top the level with distilled water.

By following these steps, you can safely disconnect and store your boat battery during the winter months, ensuring that it remains in good condition for the next boating season.

Frequently asked questions