Adding Antifreeze To Boat Engines: A Step-By-Step Guide

Adding antifreeze to a boat engine is an important step in winterizing your boat, as it prevents the need for costly repairs and extends the life of your engine. The process involves circulating antifreeze throughout the engine's cooling system to prevent residual water from freezing and causing cracks. There are two types of antifreeze: automotive antifreeze, which is suitable for boats with closed, freshwater cooling systems, and non-toxic antifreeze made from propylene glycol, which is recommended for most boats with raw water cooling systems. The procedure for adding antifreeze varies depending on the type of engine, such as sterndrive or inboard, and it is important to refer to the engine manual for specific instructions.

Choose the right antifreeze for your boat engine

Choosing the right antifreeze for your boat engine is essential to ensure effective winterization and protection from freezing temperatures. Here are some detailed guidelines to help you make the right choice:

Types of Antifreeze

There are two main types of antifreeze:

• Automotive Antifreeze: This type is commonly used in cars and is suitable for boats with a closed, freshwater cooling system. It is often made with ethylene glycol, which is highly toxic. While it can be effective in cars, it is not the best choice for boats due to its toxicity.
• Non-Toxic Antifreeze: This type of antifreeze is made from propylene glycol, which is biodegradable, odorless, tasteless, and non-toxic. It is a safer and more environmentally friendly option for marine use. This type of antifreeze is ideal for winterizing potable water systems, sanitation systems, cooling systems, and non-running boat engines.

Temperature Ratings

When selecting antifreeze, you will come across different temperature ratings, such as -50°F, -60°F, or -100°F. These ratings indicate the "burst point," which is the temperature at which a sealed copper pipe filled with the undiluted product will burst. Choose the antifreeze with a burst point that meets the needs of your local climate.

Engine Compatibility

It is crucial to consider the type of cooling system your boat engine has. Most boats have a raw water cooling system, where seawater is pumped directly through the engine to cool it. In this case, you must use non-toxic antifreeze to prevent any environmental harm. If your boat has a closed, freshwater cooling system, you can use automotive antifreeze.

Additives

Some antifreeze products contain additive packages that prevent corrosion and breakdown at high operating temperatures. These antifreeze-coolant combinations can be used for freeze protection in winter and as engine coolant in summer. However, they are not suitable for potable water system winterization.

Dilution Ratio

When using antifreeze, carefully follow the manufacturer's instructions for dilution ratios. The ethylene or propylene glycol content can vary, and higher concentrations are typically required for lower-temperature protection. Be mindful that cheapest isn't always the best option; carefully consider the dilution ratio and temperature protection offered by different products.

Prepare your engine for winter

Winterizing your boat engine is essential to prevent costly repairs and extend the life of your engine. Here are the steps to prepare your engine for winter:

Step 1: Clean Fuel and Filters

Start by filling your fuel tank and adding a fuel stabilizer. This will prevent varnish buildup in fuel lines, carburetors, or fuel injectors during the winter. It's also a good idea to replace the filter element in your fuel filter-water separator.

Step 2: Add Antifreeze

The next step is to winterize the engine block with antifreeze to prevent residual water from freezing and cracking your engine block. There are two types of antifreeze: automotive antifreeze (ethylene glycol) and non-toxic antifreeze (propylene glycol). Automotive antifreeze is highly toxic and should only be used in boats with a closed, freshwater cooling system. For most boats with a raw water cooling system, it is recommended to use a non-toxic variety. Choose an antifreeze with a high concentration, such as -100, to ensure maximum protection.

To add antifreeze to your engine, follow these steps:

• If your boat is in the water, close the intake seacock.
• Fill a five-gallon bucket with undiluted non-toxic antifreeze.
• 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.
• Secure the intake hose back on the seacock.

Step 3: Fog the Engine

Fogging the engine is an important step to protect the internal components during storage. You can use fogging oil or light motor oil for this step. Spray the fogging oil into the carburetor until the engine stalls or begins to emit white smoke. Alternatively, you can remove the spark plugs and spray the fogging oil directly into each combustion chamber.

Step 4: Change Engine and Transmission Oil

Changing the engine oil and transmission oil is crucial before storing your boat for the winter. Old, dirty oil can contain contaminants and acids that can damage the engine. Run the engine for a few minutes to warm up the oil, then shut it off and change the oil and filter. Restart the engine and run it for about a minute to circulate the fresh oil.

Step 5: Check and Maintain the Exhaust System

Break the exhaust loose from the water lift muffler or exhaust manifold and inspect for carbon buildup or corrosion. Remove the raw water injection hose from the injection nipple and check for any blockages. Check all hoses for softness, bulging, or cracking, paying extra attention to the hot side of the exhaust and cooling systems. Ensure all hose clamps are tight and look for signs of corrosion.

Step 6: Seal Engine Openings

Seal all openings that lead to the engine to prevent damp air from getting inside. You can use plastic containers and tape to cover the air inlet, transmission, crankcase breathers, and exhaust outlets. Don't forget to make a note of all the openings you have sealed so you can uncap them when spring arrives.

Understand the difference between antifreeze and coolant

While the terms coolant and antifreeze are often used interchangeably, they are not the same thing. Antifreeze is the basic ingredient that needs to be mixed with water to create coolant. Coolant is the mixture that you will find in the cooling systems of all "water-cooled" vehicles.

Antifreeze is made of ethylene glycol or propylene glycol. It has a freezing point of zero degrees, but when mixed with water at a 50-50 ratio, it lowers the freezing point to minus 35 and raises the boiling point to 223 or higher. This mixture provides sufficient cooling for engines that operate at over 200 degrees and prevents freezing in temperatures of 30 degrees below zero or lower.

Water alone is not a good option for cooling systems because it boils at 212 degrees and freezes at 32. It can also cause rust in the cooling system parts. However, water is an excellent carrier of heat and is not too corrosive.

Antifreeze, on the other hand, is not very good at carrying heat, but it won't freeze until temperatures are very low. It also flows at very low temperatures and is not corrosive.

When buying antifreeze, it is important to check the label to see if it needs to be diluted with water or if it is already premixed. It is also important to note that different vehicles require different blends of water and antifreeze, so it is crucial to check the vehicle's owner's manual for the correct type and mix.

Drain the engine coolant

Draining the engine coolant is an important step in the process of winterizing your boat engine. This procedure helps to prevent freeze damage and ensures the engine is ready for the cold season. Here is a detailed guide on how to effectively drain the engine coolant:

Prepare the Necessary Tools and Materials:

Before you begin, make sure you have the right tools and materials on hand. You will need a flat catch pan, such as an oil change pan, to collect the drained coolant. It is also recommended to have a sealable container, such as an old coolant jug, to safely store the waste coolant for proper disposal. Additionally, a shop vacuum is optional but can be useful for removing any remaining coolant from the engine.

Locate the Engine Drain Plug:

Refer to your boat's engine manual to identify the location of the engine drain plug. This plug is typically found near the bottom of the engine and may be labelled as "Block Drain" or "Coolant Drain." It may be tricky to spot, as it can blend in with other components, so take your time to find it.

Position the Catch Pan:

Place the catch pan under the plug opening, ensuring it is positioned correctly to catch any overshoot. Make sure the pan is large enough to capture all the coolant. If you anticipate the pan filling up before the draining process is complete, have additional pans ready to swap out as needed.

Slowly Open the Drain Plug:

Once you have located the drain plug, slowly open it to allow the coolant to flow out. If the flow of coolant is low, you can open the coolant fill cap at the top of the engine to facilitate the drainage. Remember to work carefully, as coolant can be toxic and should not be allowed to spill into the bilge or overboard.

Manage the Drainage Process:

As the engine coolant drains, you may need to stop and empty the catch pan into the waste storage jugs. Continue this process until the engine has thoroughly drained. Remember that there are a lot of jackets, crevices, and the heat exchanger to empty, so let it drain for an adequate amount of time.

Optional: Use a Shop Vacuum for a More Thorough Drainage:

If you want to ensure that all remaining coolant is removed, you can use the exhaust/blower side of a shop vacuum. Place the hose on the fill cap hole and seal any gaps with rags or your hand to create more effective pressure. This step will help blow out any coolant that may be lingering in the engine.

Transfer Waste Coolant to Storage Bottles and Dispose of Properly:

Once you have collected the waste coolant, transfer it to the storage bottles. Properly disposing of waste coolant is crucial. Contact your local sanitation department or trash hauler for specific disposal instructions. Many marinas also have designated disposal areas for waste coolant and other toxic waste products.

Consider Rinsing and Refilling the Engine:

If you plan on replacing the coolant with fresh coolant, it is recommended to rinse the engine first. After draining the old coolant, fill the engine with fresh water and run it for a few minutes to circulate and rinse the system. Then, repeat the drainage process before refilling with fresh coolant. Remember to refer to your boat's engine manual for guidelines on the type of coolant to use and the correct proportion of water to coolant for optimal performance and protection.

Dispose of waste coolant properly

Proper disposal of waste coolant is crucial, as it contains harmful chemicals that can pose a risk to the environment and human health. Here are some detailed, direct, and instructive guidelines on how to dispose of waste coolant properly when adding antifreeze to your boat engine:

• Collection: When draining engine coolant or flushing your engine with fresh water after winterizing, use a flat catch pan, such as an oil change pan, to collect the waste coolant. Make sure the pan is large enough to catch all the fluid and is positioned to catch any overshoot.
• Storage: Transfer the collected waste coolant into sealable containers for storage and transportation. Old coolant jugs are perfect for this purpose. Ensure that the containers are properly labelled and sealed to prevent leaks and accidental usage.
• Disposal: Waste coolant should not be dumped down drains or thrown into regular trash bins. Contact your local sanitation department, trash hauler, or marina office for disposal instructions. Many marinas have designated disposal areas for waste oil, coolant, and other toxic waste products. If you are not working near a marina, take the waste coolant to an appropriate disposal facility, such as a municipal or regional household hazardous waste handling centre. Some service stations may also accept waste coolant.
• Recycling: Propylene glycol, a common component in boat antifreeze, can be recycled, but this is typically done in industrial volumes. While some collection centres may recycle small amounts, it may be challenging to find a recycler for a gallon or two.
• Safety: Always handle waste coolant with care. Engine coolant, in particular, is highly toxic and can cause blindness or even death. It may also have a sweet taste and smell that attracts children and pets. Do not leave it unattended or within their reach.
• Absorbent Materials: When working on your boat engine, use oil-only absorbent pads to catch any drips or small spills. This will help contain the waste coolant and make cleanup easier.
• Spill Prevention: Use small containers for hazardous fluids to minimize the risk of spills. Keep these containers near the centre of the boat to reduce the chances of an overboard spill.
• Bilge Pump and Scuppers: Before performing any maintenance, remember to temporarily disable your bilge pump and plug all scuppers to prevent the accidental discharge of hazardous fluids into the water.
• Local Regulations: Stay informed about local regulations and proper waste disposal procedures in your area. Visit websites like www.earth911.com to learn about specific waste disposal guidelines and locations.

By following these guidelines and staying mindful of environmental and safety concerns, you can ensure that waste coolant is properly disposed of when adding antifreeze to your boat engine.

Frequently asked questions