Winterizing Boat Engines: Essential Steps For I/O Owners

Winterizing a boat I/O engine is essential to prevent damage and ensure smooth sailing when the weather warms up. The process involves several steps, including flushing and draining the engine, stabilizing fuel, fogging the engine, and changing the engine oil. It's also important to prepare the boat's interior and exterior, as well as the trailer, for storage during the cold months. By taking the time to properly winterize your boat, you'll save yourself from costly repairs and headaches when spring arrives.

Fill the tank with gas to prevent condensation

Filling your boat's fuel tank is an important step in winterizing your boat's I/O engine. Leaving a large volume of air in the tank increases the possibility of condensation forming, which can cause water to taint the system. This can lead to severe problems for your engine.

Condensation occurs when the air in the tank comes into contact with the cold metal of the tank, causing the moisture in the air to condense and form water droplets. By filling the tank with gas, you reduce the amount of air in the tank and decrease the chances of condensation forming.

It is recommended that you fill the tank with fresh fuel so that it is almost full, leaving a little capacity to accommodate the expansion of the fuel if the temperature warms up. This will ensure that there is no room for condensation to form and will also help to prevent corrosion in the tank.

In addition to filling the tank, it is also important to add a fuel stabilizer to the tank. This will help to prevent varnish and gunk buildup in the fuel lines, carburetors, and fuel injectors during the long period of inactivity.

By taking these steps, you can help ensure that your boat's engine will be healthy and ready for use when the warm weather returns.

Add a fuel stabiliser to the tank

Adding a fuel stabiliser to your boat's tank is a crucial step in winterising your boat's engine. Fuel stabilisers are preventative treatments that stop the chemical reactions of instability from starting in your fuel. They prevent the fuel from breaking down and oxidising, which can lead to varnish-like deposits, corrosion, and gum build-up in the system. This, in turn, can cause starting problems, reduced engine life, and poor running performance.

When choosing a fuel stabiliser, it is important to select one that is suitable for the type of fuel you use. Most gasoline today contains about 10% ethanol, identified as E10 at the pump. Ethanol is hygroscopic and hydrophilic, meaning it attracts and absorbs water molecules. This can lead to phase separation, where the ethanol/water mixture separates from the gasoline and sinks to the bottom of the fuel tank, causing major problems for your engine. A good fuel stabiliser will slow the rate at which ethanol absorbs water and reduce the possibility of phase separation.

It is also important to use the correct dose of fuel stabiliser. The dose will depend on the size of your fuel tank and the length of time you plan to store your boat. For example, if you are using Sta-Bil Fuel Stabiliser and plan to store your boat for up to 24 months, you will need to use 60 ml of stabiliser for every 9.5 litres of fresh fuel.

To add the fuel stabiliser, fill your tank with fresh fuel to about 95%, and then add the correct dose of stabiliser. Run your engine for several minutes after adding the stabiliser to ensure that the entire fuel system is treated, not just the fuel tank.

By taking the time to add a fuel stabiliser to your boat's tank, you can help protect the longevity of your engine and ensure that it is ready for use when the winter is over.

Add antifreeze to the engine

Adding antifreeze to your boat engine is a crucial step in winterizing your boat. It is important to use a non-toxic, propylene glycol-based antifreeze, as this will be safer for the environment when you start your boat back up in the spring. Avoid ethylene-based antifreeze, as it can release toxins into the water.

The process of adding antifreeze to your engine will depend on whether your boat has a sterndrive or an inboard engine. Sterndrives need to be treated like inboard engines but with a few additional steps to protect the lower parts.

If your boat has a sterndrive, begin by connecting your garden hose to a faucet and hooking it to a motor flusher. Place this over the raw water intake, turn on the freshwater, and start your boat's engine. Let the engine warm up to operating temperature so the thermostat will open and let coolant circulate through the entire engine. This is also important as it lets the fuel stabilizer circulate through all fuel lines, carburetors, or injectors.

Once your engine is warm, turn it off and hook up a winterizing kit to the motor flusher, in place of your garden hose. You will then need to remove the flame arrestor from the carburetor.

Start the engine again and open the valve to the tank of the winterizing kit. You should begin to see antifreeze discharging from the exhaust. When the tank is almost empty, begin spraying fogging oil into the carburetor. This will usually cause lower-horsepower engines to stall, while higher-horsepower engines may continue running while emitting white smoke. Spray a generous amount of fogging oil, then turn the engine off. Alternatively, you can remove the spark plugs and spray the fogging oil directly into each combustion chamber.

For inboard engines, you will need a five-gallon bucket and enough antifreeze for your engine and related plumbing (at least two gallons). If your engine takes a lot of antifreeze, you may need a helper to add more antifreeze to the bucket as needed. If your boat is in the water, close the intake seacock.

Remove the raw water intake hose from the seacock and insert the end into the antifreeze in the bucket. Start the engine and run it at idle until antifreeze discharges from the exhaust outlet for 30 seconds or more. When the bucket is almost empty, begin fogging the carburetor. Spray plenty of mist into the engine as it coughs and splutters, then turn off the ignition when the antifreeze runs out. Secure the intake hose back onto the seacock.

Change the engine oil

Changing the engine oil is an important step in winterizing your boat to ensure the engine is healthy and ready to go in the spring. Here is a detailed, step-by-step guide:

First, it is important to warm up the engine. This is done by running the engine while the boat is in the water or by using an adaptor or motor muffs with a hose running the water supply. Warming up the engine helps to get the dirty oil to drain out more effectively and flush out any impurities.

Next, you will need to drain the old engine oil. Locate the drain plugs, which are usually found in the engine block and manifold, and remove them. Be careful, as the engine will be hot and hot water will gush out. You may also need to remove the water pump hose to drain the oil completely.

Once the old oil has been drained, it's time to add new oil. Use high-quality oil and filters as recommended by your engine's manufacturer. Top up the oil until the level is above the minimum and below the maximum, as indicated on the dipstick.

If you are unable to change the oil, it is recommended to add a crankcase oil stabilizer before beginning the winterizing process. This will help protect the engine until you are able to change the oil.

Changing the engine oil is crucial as it removes contaminants and acids that can harm the engine during winter storage. Old oil can contain moisture, which can cause excessive wear and lead to possible engine failure. Additionally, the oil may become contaminated with dirt and particles, which can be harmful if not dealt with properly.

By following these steps, you can help ensure your boat's engine is protected and ready for use when the warm weather returns.

Drain the engine

Draining the engine is a crucial step in winterizing your boat to prevent water in the cooling chambers from freezing and causing damage. This process is necessary for inboard and sterndrive engines, as outboards self-drain.

First, locate and open the petcocks or bronze plugs similar to bilge plugs underneath the manifolds and on the sides of the engine block. Some engines may have knock sensors in the drain location, which must be carefully removed. You may need to use a short, stiff piece of wire to break up any rust scale and ensure the engine drains completely.

Next, remove the water pump hose from the bottom of the water pump to allow it to drain fully. If your engine has a seawater pump, remove both hoses from the pump.

If your engine is raw water-cooled, you must also drain the water from the exhaust manifolds. On older engines, this can be done by removing the drain plugs from the rear of each manifold. Newer engines may have a hose with a quick-disconnect fitting that connects the manifolds, which should be uncoupled and drained.

Finally, disconnect the large diameter hose that runs from the water circulating pump to the thermostat housing, ensuring all water drains from the hose.

Frequently asked questions