Winterizing Your 350 Boat Engine: A Step-By-Step Guide

Winterizing a 350 boat engine is crucial to protect it from freezing temperatures, corrosion, and damage caused by extended inactivity. This process involves several steps, including flushing the cooling system, protecting the fuel system, lubricating components, and changing engine oil and filters. It is important to refer to the owner's manual for specific instructions and recommendations. Additionally, it is essential to prepare the boat for storage by covering it and ensuring proper ventilation. Proper winterization ensures the engine's longevity and performance, making it ready for the next boating season.

Prepare your engine for winterizing

Before you winterize your engine, it's important to prepare your engine for the process. Here are some steps you can take to get ready:

• Consult your owner's manual: Refer to your outboard's owner's manual for specific instructions and recommendations. Different engines may have different requirements, so it's important to check.
• Safety first: Ensure you are working in a well-ventilated area and handle fuel carefully. It is also recommended to disconnect the battery before beginning any work.
• Fill the tank with gas: Filling the tank helps to decrease the chance of getting air into the tank, which can cause moisture and condensation issues in low temperatures.
• Add a fuel stabilizer: Using a product like STAR BRITE EZ-To-Start Fuel Additive will prevent buildup in your boat's fuel lines, injectors and carburetors while it sits idle for long periods.
• Warm up the engine: You can do this 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.
• Do a final inspection: Check your exhaust system for corrosion and your hoses and hose clamps for any damage.

Now that your engine is prepared, you can move on to the next steps of the winterization process, including adding antifreeze and spraying fogging oils, changing the engine oil and filter, and other necessary maintenance tasks.

Add antifreeze and spray fogging oil

To add antifreeze to your 350 boat engine, 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 also need a helper to add more antifreeze to the bucket as needed.

• Fill a five-gallon bucket with undiluted non-toxic antifreeze.
• If your boat is in the water, close the intake seacock.
• Remove the raw water intake hose from the seacock. This step can be challenging, as hose clamps and hoses may be mechanically frozen in place.
• Insert the hose into the antifreeze in the bucket.
• Start the engine and run it at idle until antifreeze discharges from the exhaust outlet for at least 30 seconds.
• For gasoline engines, fog the cylinders, which should cause the engine to stop.
• Secure the intake hose back onto the seacock.

Now, to spray fogging oil:

• Remove the flame arrestor from the carburetor.
• Start the engine and open the valve to the tank of the winterizing kit.
• Watch the antifreeze level drop in the tank.
• 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, remove the spark plugs one at a time and spray the fogging oil directly into each combustion chamber.

Fogging oil is an anticorrosive agent that will protect the internal surfaces of the carburetor and the cylinders.

Change the engine's oil and replace the filter

Changing the oil and replacing the filter on a 350 boat engine is a crucial step in winterizing your boat and maintaining your engine. Here is a detailed guide to walk you through the process:

Preparation:

Before beginning the oil change, there are a few important preparations to make. Firstly, ensure you have purchased the correct type and amount of engine oil as specified in your boat's manual. Gather all the necessary tools, including an oil extractor, catch pans, and oil-absorbent pads. Place these beneath the engine and oil filter to catch any accidental spills and protect the bilge. If your boat is in the water, you will need to close the intake seacock.

Warm Up the Engine:

It is recommended to change the engine oil when the engine is warm from operation. Warm oil flows more freely and carries away more impurities. Run the engine for a few minutes to warm up the oil and lower its viscosity. This will allow the oil to pick up more contaminants, ensuring a more thorough cleaning.

Drain the Old Oil:

After warming up the engine, shut it off and proceed to drain the old oil. You can use an oil extractor or an oil evacuation system to remove the oil. If your boat is equipped with a dipstick tube, a portable, manual, or electric vacuum pump can be used to extract the oil. Place a catch pan beneath the engine to collect the drained oil.

Inspect the Old Oil:

Once the oil is drained, take a moment to inspect it. Milky oil can indicate the presence of water, antifreeze, or fuel, which could be a sign of a blown gasket or a cracked block. Rub some of the old oil between your fingers; if it feels abrasive or has a burnt odour, it may be a sign of bearing wear or old oil.

Change the Oil Filter:

The next step is to change the oil filter. Drip-free filter replacement can be challenging, so it is important to place oil pads or a catch pan beneath the filter before removing it. You can also place a large zip-top bag around the filter during removal to reduce the chance of spills. Remove the old filter carefully and replace it with a new one. Lubricate the O-ring at the top of the new filter with a small amount of new oil.

Add New Engine Oil:

Now, you can add new engine oil to the engine. Refer to your boat's manual for the specific type and amount of oil required. Use a funnel to make this process easier, and add oil until it reaches the "Full" or "OK" range mark on the dipstick. Recheck the oil level and top it off if needed.

Restart the Engine:

After adding the new oil and replacing the oil filter, restart the engine and run it for about a minute. This will circulate the fresh oil to internal parts and ensure that the new filter is filled. While the engine is running, carefully inspect for any leaks, especially around the oil pan and filter.

Final Checks:

Once you have completed the oil change and restarted the engine, there are a few final checks to make. Ensure that the oil filter is not leaking and that the oil level is correct. Top up the oil if necessary. Dispose of the waste oil and used oil pads properly, following local regulations and guidelines.

By following these steps, you can effectively change the oil and replace the filter on your 350 boat engine, ensuring its optimal performance and longevity.

Flush the cooling system

Flushing the cooling system is an essential step in winterizing a 350 boat engine. This process helps to remove any salt, sand, or other debris that could cause corrosion and blockages in the engine. Here is a detailed guide on how to flush the cooling system:

Firstly, attach the flushing muffs to the water intakes of your boat engine, ensuring a snug fit. Flushing muffs are an essential tool for this process as they allow you to circulate fresh water through the engine without having to start the engine.

Next, connect a garden hose to the flushing muffs. Ensure that your water supply is turned on and start the engine. Allow the engine to run for at least 10 minutes, circulating fresh water through the cooling system. This will help to remove any salt, sand, or debris that has built up in the system.

After 10 minutes, turn off the engine and then the water supply. Now, you can remove the flushing muffs.

If your boat is equipped with a sterndrive, there are a few additional steps to take. A sterndrive is an inboard engine with an outboard drive system, so it requires some extra attention. To drain the lines, leave the sterndrive stored in a down position. Use your freshwater source (boat hose and faucet) to allow the engine to reach the operating temperature. This will open the thermostat, allowing the coolant and fuel stabilizer to circulate through the lines, carburetors, and injectors.

It is important to note that the process of flushing the cooling system may vary slightly depending on the specific type and model of your boat engine. Always refer to your owner's manual for detailed instructions and recommendations specific to your boat.

Additionally, remember that winterizing your boat engine also involves other crucial steps such as changing the engine oil and filter, stabilizing the fuel system, and protecting internal engine components. By following a comprehensive winterization process, you can ensure that your boat engine is protected from freezing temperatures, corrosion, and damage caused by extended inactivity during the winter months.

Fuel system protection

Stabilizing the Fuel:

• Add the recommended amount of fuel stabilizer to your fuel tank. Fuel stabilizers prevent the fuel from degrading and ensure that your engine starts easily in the spring.
• Run the engine for a few minutes to circulate the stabilizer throughout the fuel system. This will help ensure that the stabilizer reaches all parts of the fuel system, including the fuel lines, injectors, and carburetor.

Draining the Fuel System:

• Run the engine until it stalls due to a lack of fuel. This will help remove any remaining fuel from the carburetor and fuel lines.
• While the engine is still warm, spray fogging oil into the carburetor and spark plug holes. This step will protect the internal components from corrosion during storage.

Additional Tips for Fuel System Protection:

• If your boat has an older, vented fuel tank, fill it with fresh fuel to prevent condensation from forming. Stop filling when the tank is about 95% full to allow for fuel expansion during temperature changes.
• If possible, use ethanol-free fuel, such as REC-90, which is specifically designed for recreational engines.
• Always store your boat with fresh fuel that has been treated with a marine fuel stabilizer. Untreated fuel can oxidize and form a gum-like substance in the engine's fuel system, especially in carburetors.
• If your gasoline contains ethanol (E10), it will absorb moisture over the winter. If it absorbs enough water, the ethanol can separate from the gasoline, creating a caustic mixture that can damage your engine.
• To prevent this "phase separation," either empty the tank or add a stabilizer to the fuel.
• Fill the tank to 95% full to allow for expansion and to reduce the amount of moist air that can be absorbed.

Frequently asked questions