Fogging An Inboard Boat Engine: A Step-By-Step Guide

Fogging an inboard boat engine is an essential part of winterizing your boat. It's a process that prevents gunk buildup and condensation in your boat's fuel tank, helping to keep the engine healthy. The fogging process involves spraying fogging oil into the engine, which protects it from corrosion. This is usually done after applying antifreeze to the engine to prevent water condensation from freezing and causing cracks. Fogging an inboard boat engine is just one of several steps in the winterizing process, which also includes filling the fuel tank, adding a fuel stabilizer, and changing the engine oil and filter.

How to Fog an Inboard Boat Engine

Warming the engine

Firstly, it is recommended to fill the boat's fuel tank before beginning the process. This helps to prevent air from getting into the fuel system, as air can contain moisture which can lead to condensation and cause engine problems.

Once the fuel tank is filled, you can proceed to warm the engine. There are two ways to do this. One way is to run the engine while the boat is still in the water. The other option is to use an adaptor or motor muffs and connect the engine to a hose running a water supply. This will help to remove any debris from the engine cooling system.

It is important to let the engine warm up to operating temperature. This will allow the thermostat to open and ensure the proper circulation of coolant, fuel stabilizer, and antifreeze throughout the engine. Warming the engine also helps to circulate the fuel and stabilizer, allowing them to protect the fuel delivery system components.

After warming the engine, you can proceed to the next steps of adding antifreeze and fogging oil, which will be covered in subsequent paragraphs. However, it is important to keep the engine running while performing these steps to ensure the proper circulation of fluids.

By following these instructions, you can effectively warm the engine of your inboard boat, ensuring that it is prepared for the fogging process and protected during the winter months.

Using antifreeze

Fogging an inboard boat engine with antifreeze is a crucial step in winterizing your boat to prevent freeze damage. Here's a detailed guide on using antifreeze to protect your engine:

Choosing the Right Antifreeze

It is important to select a non-toxic, propylene glycol-based antifreeze to avoid releasing toxins into the water. Opt for a premium "virgin" antifreeze with corrosion inhibitors to protect your engine and cooling system. Choose an antifreeze with the highest concentration available, typically -100 degrees, to account for any residual water inside the engine, which can dilute the solution.

Draining the Cooling System

Before adding antifreeze, it is essential to drain the cooling system. Allow the engine to cool down, then locate and remove the drain plugs from the engine block and exhaust manifolds. Disconnect the hoses from the engine's water pump and exhaust system to facilitate drainage. Keep a bucket nearby to collect the drained water and inspect hoses and clamps for any damage. Once the system is drained, reinstall the plugs and reconnect the hoses securely.

Adding Antifreeze

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 and insert it 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. Ensure you have enough antifreeze to fill the engine and related plumbing; you may need a helper to add more antifreeze to the bucket as needed.

Fogging the Engine

While the engine is still warm, locate the carburetor or fuel injection system. For a carbureted engine, spray fogging oil directly into the carburetor while the engine is running. Do this gradually to avoid overwhelming the engine. For a fuel-injected engine, follow the manufacturer's instructions, typically involving removing the air filter and spraying the fogging oil into the throttle body to reach all cylinders. Let the engine run for another minute to spread the oil throughout the internal components. Finally, shut off the engine, remove the spark plugs, and spray a small amount of fogging oil into each cylinder. Manually turn the engine over a few times to distribute the oil evenly, then reinstall the spark plugs.

Final Steps

After fogging the engine, there are a few additional steps to complete the winterization process. Change the engine oil and oil filter to remove any contaminants and acids that can harm the engine during storage. Check the exhaust system for carbon buildup or corrosion, and inspect the raw water injection hose for any blockages. Seal all openings to the engine to prevent damp air from getting inside, and create a list of sealed openings to remember to uncap them in the spring. If your boat will be stored in the water, tighten the stuffing box to eliminate dripping, and leave a reminder to readjust it when the season begins.

Spraying fogging oil

To spray fogging oil into an inboard boat engine, you can follow these steps:

• Warm the engine: This can be done by running the engine while the boat is still in the water or by using an adaptor or motor muffs with a hose running the water supply. Warming the engine helps to circulate the fuel and stabilizer, enhancing their effectiveness in protecting the fuel delivery system.
• Apply antifreeze: Adding antifreeze to the engine prevents water condensation and freezing, which can lead to expansion and cracks. Use a non-toxic propylene glycol antifreeze instead of ethylene-based antifreeze to avoid releasing toxins into the water.
• Spray fogging oil into the engine: While the engine is still warm, spray a generous amount of fogging oil into the engine. You may notice white smoke, which indicates that you are successfully coating the engine components.
• Remove spark plugs (optional): Alternatively, you can remove the spark plugs and spray the fogging oil directly into the engine's combustion chamber. This method does not require the use of antifreeze.

When spraying fogging oil, it is important to be generous and not hold back, especially if you plan on storing your boat for a long time. This will ensure that all vulnerable components are adequately protected.

Changing the oil

Step 1: Prepare for the Oil Change

Firstly, you will need to purchase the correct type and amount of oil for your engine. It is also important to gather the necessary tools, which may include an oil extractor, a manual or electric pump, oil-absorbent pads, and a funnel. Place catch pans and oil-absorbent pads beneath the engine and oil filter to prevent accidental spills.

Step 2: Warm Up the Engine

Before changing the oil, it is recommended to warm up the engine to operating temperature. Warm oil drains more easily and holds more contaminants in suspension, meaning more impurities will be removed when the oil is changed.

Step 3: Drain the Old Oil

Inboard marine engines typically have little to no access to the oil pan drain plug, so an oil evacuation system or oil extractor pump is often required. Remove the oil either via the dipstick tube or the drain plug, if accessible. If using a pump, attach it to the dipstick tube or a bulkhead and pump the oil out into a container. If your engine has a drain plug, you can also use a foil roasting pan to catch the oil, placing a piece of thin plywood underneath to keep the pan rigid.

Step 4: Inspect the Old Oil

Once the oil is drained, it is a good idea to inspect it for any issues. Oil that appears milky may indicate the presence of water, antifreeze, or fuel, which could be a sign of a blown gasket or cracked block. Rubbing a small amount of oil between your fingers can also help identify issues; if it feels abrasive or has a burnt odour, it may indicate bearing wear.

Step 5: Remove and Replace the Oil Filter

It is recommended to replace the oil filter each time you change the oil. Place oil pads or a catch pan beneath the filter to catch any spills, or use a zip-top bag around the filter during removal. Remove the old filter with an oil filter wrench and install a new one, tightening it according to the manufacturer's instructions.

Step 6: Add New Oil

Once the old oil is drained and the new filter is installed, add new oil to the engine. Use a funnel to make this process easier, and add oil until you reach the recommended level specified in your engine manual.

Step 7: Check for Leaks

After adding the new oil, start the engine and check for any leaks, especially around the oil pan and filter. Top up the oil if necessary, as the new filter will now be filled.

By following these steps, you can ensure that your inboard boat engine has clean oil and is ready for winter storage or continued use.

Final checks

Now that the engine is fogged and ready for winter, there are a few more jobs to do to ensure your boat is properly winterized.

Firstly, check the exhaust system for any signs of carbon buildup or corrosion. Disconnect the exhaust from the manifold or water lift muffler and inspect the hose and exhaust system. It is important to remove these surface contaminants before storing your boat for winter.

Next, inspect all hoses and hose clamps for any damage. Look for signs of cracking, shredding or rust. Hoses are a common point of ingress for moisture, so it is important to replace them if they are damaged.

Seal all engine openings to prevent damp air from getting inside. Make caps out of plastic containers and tape them over the air inlet, transmission and crankcase breathers, and exhaust outlets. Leave a note for yourself listing all the openings you have sealed, so you remember to uncap them in the spring.

Finally, give the boat a once-over and perform any other necessary tasks. This includes things like lubricating all joints and grease points on the motor, removing control cables, and covering the boat with a quality boat cover. You may also want to use pest controls and repellents, invest in a dehumidifier, and regularly check on the boat over the winter.

Frequently asked questions