Draining Antifreeze From Your Boat Engine: A Step-By-Step Guide

Draining antifreeze from a boat engine is a routine maintenance task that should be done at most once a year. It is important to do this correctly to avoid damaging your engine. This is because water left inside the engine can freeze and expand, causing cracks. There are two methods for draining antifreeze: using a plug or valve at the bottom of the engine, or simply starting the engine and letting the antifreeze come out with the raw water exhaust. It is important to capture the waste antifreeze and dispose of it properly.

How to drain antifreeze from a boat engine in the water

Draining antifreeze from your boat engine is a routine maintenance task that should be done about once a year. While it is possible to pay someone to do it, it is not a difficult task to do yourself. Here is a step-by-step guide on how to drain antifreeze from a boat engine while it is in the water.

Step 1: Prepare the Necessary Tools and Containers

Before you begin, gather the following tools and containers:

• A flat catch pan, similar to an oil change pan, to collect the drained antifreeze.
• A sealable container, such as an old coolant jug, to hold the waste antifreeze.
• Optionally, a shop vacuum to help with the draining process.
• The engine manual for your boat, which you can refer to for specific instructions and to locate the engine drain plug.

Step 2: Locate the Engine Drain Plug

Near the bottom of the engine, you will find the engine drain plug. It may be tricky to find, as it can look like another knobby part of the engine. Refer to the engine manual for help. Engine coolant drains are usually identified in the engine diagram and may be labeled as "Block Drain" or "Coolant Drain."

Step 3: Place the Pan Under the Plug Opening

Position the flat catch pan under the plug opening, making sure it is big enough to catch all the antifreeze and placed to catch any overshoot.

Step 4: Open the Drain Plug

Slowly open the drain plug to allow the antifreeze to flow into the pan. If the flow is low, you may need to open the coolant fill cap at the top of the engine.

Step 5: Manage the Drain Pan

If the drain pan gets full, close the plug, empty the pan into the sealable container, and then replace the pan under the drain to continue.

Step 6: Let the Engine Drain

Let the engine drain completely. There are a lot of jackets and crevices, as well as the heat exchanger, that need to empty. This may take some time, and a lot of antifreeze may dribble out.

Step 7: (Optional) Use a Shop Vacuum

If you have a shop vacuum, you can use the exhaust/blower side to put the hose on the fill cap hole and blow out any remaining antifreeze. You may need to seal the gap between the hose and the fill cap hole with rags or your hand to get better pressure.

Step 8: Transfer Waste Antifreeze to Storage Bottles

Transfer the waste antifreeze from the catch pan and/or sealable container into storage bottles for proper disposal.

Step 9: Dispose of Waste Antifreeze Properly

Properly dispose of the waste antifreeze. Do not dump it down the drain or throw it in the trash. Contact your local sanitation department or trash hauler for disposal options. Many marinas have disposal areas for waste antifreeze, or you can take it to an appropriate disposal facility or service station.

Additional Notes:

If you are replacing the antifreeze with fresh antifreeze, it is recommended to fill the engine with fresh water and run it for a few minutes to circulate and rinse it before refilling with fresh antifreeze.

While antifreeze is non-toxic, it is still better to collect and dispose of it properly. Recapturing your antifreeze can be done before or after launching your boat. If your exhaust outlet is low near the water or hard to reach from the dock, it may be more practical to recapture the antifreeze before launching.

How to drain antifreeze from an outboard boat engine

Draining antifreeze from your outboard boat engine is a routine maintenance task that should be done at most once a year. While you can pay someone to do it, it is not necessary. Here is a step-by-step guide on how to drain antifreeze from your outboard boat engine:

Step 1: Prepare the Necessary Tools and Containers

Before you begin, gather the following tools and containers:

• A flat catch pan, such as an oil change pan
• A sealable container to hold the waste antifreeze; old antifreeze jugs are perfect for this
• Optional: a shop vacuum
• A bucket of undiluted non-toxic antifreeze (at least two gallons)
• Additional antifreeze if your engine takes a lot or if you are doing this for the first time

Step 2: Locate the Engine Drain Plug

Refer to the engine manual in your owner's manual to find the engine drain plug. It is usually located near the bottom of the engine and may be tricky to find as it can look like another knobby part of the engine. Engine coolant drains are typically identified in the engine diagram and may be labeled "Block Drain", "Coolant Drain", or something similar.

Step 3: Place a Pan Under the Plug Opening

Position the pan under the plug opening to catch any antifreeze that will come out. Make sure the pan is big enough to catch all the antifreeze and is placed to catch any overshoot.

Step 4: Open the Drain Plug

Slowly open the drain plug to allow the antifreeze to flow out. If the flow is low, open the coolant fill cap at the top of the engine. If the drain pan gets full, close the plug, empty the pan into the waste storage jugs, and then replace it under the drain.

Step 5: Let the Engine Drain

Let the engine drain completely. There are a lot of jackets and crevices, as well as the heat exchanger, that need to empty. This may take some time, and a lot of antifreeze may dribble out.

Step 6: Optional: Use a Shop Vacuum

If you have a shop vacuum, you can use the exhaust/blower side to put the hose on the fill cap hole and blow out any remaining antifreeze. You may need to seal the gap between the hose and the fill cap hole edge with rags or your hand to get more effective pressure.

Step 7: Transfer Waste Antifreeze to Storage Bottles

Once the engine has finished draining, transfer the waste antifreeze from the pan into the storage bottles.

Step 8: Dispose of Waste Antifreeze Properly

Dispose of the waste antifreeze properly. Do not dump it down the drain or throw it in the trash. Contact your local sanitation department or trash hauler for more information on proper disposal. Many marinas also have disposal areas for waste antifreeze.

Step 9: Refill with Fresh Antifreeze (Optional)

If you are replacing the antifreeze with fresh antifreeze, it is recommended to fill the engine with fresh water and run it for a few minutes to circulate and rinse it. Then, when the engine has cooled down, repeat steps 2 through 6 before refilling with fresh antifreeze.

Additional Tips:

• Always use non-toxic antifreeze for your boat engine. Boat antifreeze is typically made from propylene glycol, which is tasteless, non-toxic, and safe to use in drinking water systems.
• When replacing engine antifreeze, check your boat's engine manual for guidelines on which type of antifreeze to use and the correct proportion of water to antifreeze. Most specify a 50%/50% mix for optimal heat removal and freeze protection.

How to drain antifreeze from an inboard boat engine

Draining the antifreeze from your inboard boat engine is a simple but necessary task. Antifreeze is used to prevent freezing in boat systems, and while it is non-toxic, it is still better to collect and dispose of it properly. Here is a step-by-step guide on how to drain antifreeze from your inboard boat engine:

Step 1: Prepare the Necessary Tools and Materials

• Flat catch pan, such as an oil change pan
• Sealable container to hold the waste antifreeze, e.g. old coolant jugs
• Optional: a shop vacuum
• Antifreeze (at least 2 gallons)
• Fogging oil

Step 2: Locate the Engine Drain Plug

Refer to the engine manual in your owner's manual to find the engine drain plug. It is usually located near the bottom of the engine and may be labelled as "Block Drain" or "Coolant Drain".

Step 3: Position the Catch Pan

Place the catch pan under the plug opening, making sure it is positioned to catch any overshoot and is big enough to catch all the antifreeze.

Step 4: Open the Drain Plug

Slowly open the drain plug. If the flow of antifreeze is low, open the coolant fill cap at the top of the engine. If the catch pan gets full, close the plug, empty the pan into the sealable container, and replace the pan under the drain before continuing.

Step 5: Let the Engine Drain

Let the engine drain completely. There are a lot of jackets and crevices, including the heat exchanger, that need to be emptied.

Step 6: Optional: Use a Shop Vacuum

Using the exhaust/blower side of a shop vacuum, put the hose on the fill cap hole to blow out any remaining antifreeze. You may need to seal the gap between the hose and the fill cap hole with rags or your hand to increase pressure.

Step 7: Transfer Waste Antifreeze to Storage Containers

Transfer the waste antifreeze from the catch pan and/or catch containers into the sealable storage containers.

Step 8: Dispose of Waste Antifreeze Properly

Dispose of the waste antifreeze at a toxic waste disposal facility, often found at your local municipal landfill. Some marinas also have disposal areas for waste antifreeze.

Step 9: Fog the Carburetor

Start the engine up again and spray fogging oil into the carburetor. This will cause the engine to cough and sputter, but it will continue running while emitting white smoke. Spray a good amount of fogging oil while the engine is running.

Step 10: Turn Off the Engine

Once the antifreeze runs out, turn off the ignition.

How to drain antifreeze from a boat engine on a trailer

Draining antifreeze from a boat engine is a routine maintenance task that should be done at least once a year. While you can pay someone to do it, it is not difficult to do yourself, as long as you follow the correct procedure. Here is a step-by-step guide on how to drain antifreeze from a boat engine while it is on a trailer:

• Set up your workspace: Park your boat trailer in a driveway or other flat, spacious area where you have easy access to a hose and can work comfortably.
• Locate the drain plugs: Before you begin the winterization process, identify where the drain plugs are. Refer to the owner's manual or do some online research to pinpoint their exact locations.
• Add fuel stabilizer: Pour fuel stabilizer into the tank to prevent the gas from deteriorating during the winter months and to ensure easier starts in the spring. Follow the instructions on the product label.
• Fill the tank with gas: Fill the fuel tank to prevent air and condensation from forming inside. Condensation can lead to water accumulation, which is not desirable in the fuel system.
• Run the boat engine: Start the engine and let it run until it reaches its normal operating temperature. This will open the thermostat and allow antifreeze to circulate through the engine.
• Fog the engine (optional): Spray fogging oil into the carburetor while the engine is still hot. This will coat the carburetor and cylinders with a thin layer of oil and cause the engine to shut off.
• Remove the drain plugs: Carefully remove each drain plug, as the engine will be hot. Have a flat catch pan or bucket underneath to collect the draining antifreeze and water.
• Clear debris: Use a thin piece of wire to poke into the drain holes and loosen any built-up debris. Be gentle to avoid damaging the holes.
• Top off the oil (if necessary): Check the oil level using the dipstick. If it is below the minimum mark, add oil until it reaches the recommended level.
• Drain hoses: Unscrew the thermostat-housing hose clamps and remove any residual water from the hoses. Check the housing inlets and outlets for corrosion and grease the metal connection points. Inspect the hoses for any leaks.
• Add antifreeze: Pour antifreeze into each hose until it starts to come out through the thermostat housing. Reinstall the hoses and tighten the hose clamps.
• Clean and organize the boat: Wipe down the interior with a boat cleaner or multi-purpose cleaner. Remove life jackets, water bottles, and other items for storage elsewhere.
• Disconnect the battery: Remove the nuts from the battery terminals and label the positive and negative wires for easy reinstallation. Bring the battery inside to a covered and climate-controlled area, and connect it to a charger.

By following these steps, you will effectively drain the antifreeze from your boat engine and prepare it for winter storage. Always refer to your owner's manual for specific instructions related to your boat's make and model.

How to dispose of antifreeze from a boat engine

Antifreeze is an essential component of boat engines, particularly during winter, to prevent water from freezing and cracking the engine as it expands. However, it is important to know how to properly dispose of antifreeze when the time comes. Here is a step-by-step guide on how to do it:

Step 1: Collect the Antifreeze

When it is time to get the antifreeze from your boat engine, usually in the spring, the process is relatively simple. Start by placing a flat catch pan, such as an oil change pan, under the engine drain plug to collect the antifreeze. Slowly open the drain plug and let the antifreeze flow into the pan. If your boat has an easy-open valve, this process will be more straightforward. Remember to capture all the waste antifreeze; you don't want it going into the bilge or overboard!

Step 2: Transfer to Sealable Containers

Once you have collected the antifreeze in the pan, transfer it to sealable containers for storage and transport. Old coolant jugs are perfect for this purpose. Make sure you have enough containers to hold all the waste antifreeze.

Step 3: Dispose of the Antifreeze Properly

Now that you have collected and stored the antifreeze, it is time to dispose of it properly. Antifreeze should never be dumped down the drain or thrown in the trash. Contact your local sanitation department or trash hauler for information on disposal options in your area. Many marinas have a designated disposal area for waste antifreeze and other toxic waste products. Ask the staff at your marina for specific instructions. If you are not based at a marina, take the antifreeze to an appropriate disposal facility, such as a service station or a municipal household hazardous waste handling centre.

Important Notes on Antifreeze

It is important to distinguish between two types of antifreeze: engine coolant (ethylene glycol) and boat antifreeze (propylene glycol). Engine coolant is highly toxic and must be handled with extreme care. It can cause blindness or even death and should never be left unattended. Boat antifreeze, on the other hand, is non-toxic, tasteless, and safe to use in drinking water systems. While it is not immediately toxic to wildlife, it is still important to collect and dispose of it properly to minimise its impact on the environment.

Frequently asked questions