Preventing Engine Freeze: Tips For Boat Owners

Keeping a boat engine from freezing is essential to prevent engine cracking and general boat motor damage. While saltwater in a boat motor freezes at 28.4°F (-2°C) or lower, freshwater freezes at 32°F (0°C) or lower. To prevent a boat motor from freezing, it is necessary to remove the boat engine from the water, drain the boat motor of all water, change the gear lube oil, spray carburetor inlets and spark plug holes, and cover the engine with a heated cover.

Remove the boat from seawater

Removing your boat from seawater is an essential step in preventing your boat motor from freezing. This process is straightforward and can be completed in approximately 15 minutes. Here's a detailed guide on how to do it:

Firstly, bring a vehicle with a trailer to a boat ramp area and back the trailer down the ramp. Move your boat from the seawater onto the trailer and ensure it is securely tied down. Haul the boat out of the water with the vehicle and park on a flat, workable area. This step is crucial as it ensures that your boat is accessible for the necessary maintenance to prevent freezing.

If you have an outboard motor, it is vital to remove it from the seawater to prevent freezing. Inboard motors are already out of the water, so this step does not apply.

When removing your boat from seawater, ensure you have a clear plan for the next steps in the winterization process. The following steps are crucial to prevent freezing and protect your boat motor: draining the boat motor of all water, stabilizing the fuel, changing the gear lube oil, spraying the carburetor inlets and spark plug holes, and finally, covering the engine with a heated blanket.

By following these steps, you can effectively prevent your boat engine from freezing, which can cause engine cracking and other costly damage.

Drain the boat motor from water

Draining the water from your boat motor is an important step in preventing your boat engine from freezing. This is because any fresh water in a boat motor will freeze at 32°F (0°C) or lower, and any salt water in a boat motor will freeze at 28.4°F (-2°C) or lower.

To drain the water from your boat motor, first trim the outboard motor to its maximum angle, typically 65 degrees. This will allow all the trapped water to be released onto the ground. Next, use a sponge to wipe around the engine and engine bay to release any remaining trapped water. Be sure to wipe around any flat horizontal surfaces around the engine where water may be trapped. This process should take approximately 5 minutes to complete.

It is important to note that if you do not drain the water from your boat motor, it can freeze and cause cracks to emerge on the engine's lower unit. This can be costly to repair and can impact the performance and safety of your boat. Therefore, it is crucial to take the time to properly drain your boat motor to prevent freezing and any resulting damage.

Additionally, if your boat is stored out of the water, it loses heat faster than a boat in the slip. To keep the engine compartment warm, cover the outdrive unit with a snap-on cover or a heavy-duty plastic bag. This will prevent heat from escaping through the exposed metal and help to keep the engine compartment warm.

Stabilise the boat fuel

To stabilise the boat fuel, you must first fill the fuel tank with fresh fuel until it's 99% full. This will ensure there is almost no space for any moisture or air, which could cause corrosion or fuel degradation. Next, add a fuel stabiliser—pouring in enough to treat 2.5 gallons of fuel with 1 ounce of stabiliser. Start the engine and let it run for 5 minutes at 1,000 rpm, so that the stabiliser can mix properly with the fuel. Finally, turn off the engine. This process will prevent the fuel from oxidising and forming a gum-like substance in the fuel tank and fuel lines, which can cause corrosion.

Change the gear lube oil

Changing the gear lube oil is an important step in preventing your boat motor from freezing. This is because any water that has entered the gear lube tank will freeze and expand as temperatures drop, causing damage to the lower unit of the boat motor. Therefore, it is necessary to drain the old oil and replace it with fresh oil.

To change the gear lube oil, first, put the engine into an upright position to allow the old oil to flow out. Place an oil pan below the motor to collect the waste oil. Next, locate the gear lube tank, which is usually found in the lower unit of the motor near the propeller. Unscrew the lower and upper gear lube tank screws using a screwdriver and allow the old oil to drain out. If the oil appears milky yellow, this is an indication that water has gotten into the tank. Ensure the tank is completely empty before pumping in fresh gear lube oil through the lower screw hole. Continue pumping until the new oil flows out of the top gear lube hole, then screw the holes back up.

The whole process of changing the gear lube oil should take around 20 minutes. It is important to consult your boat motor owner's manual for specific instructions, as the procedure may vary slightly depending on the make and model of your boat.

By taking the time to change the gear lube oil, you can help prevent freezing and ensure the longevity of your boat motor.

Cover the engine with a heated blanket

Covering your boat engine with a heated blanket is a good way to prevent it from freezing. This method is also one of the fastest ways to prevent a boat motor from freezing. It only takes about 2-3 minutes to wrap a heated blanket around the engine, ensuring that there are no areas left uncovered.

However, it is important to note that some sources advise against using an electric blanket on the engine, citing the risk of sparks from the thermostat as it makes and breaks. This can be dangerous if there are gasoline fumes present in the engine compartment.

To avoid this risk, one suggestion is to use a heated blanket that has a length of cord between the blanket and the on/off/thermostat controller. This way, the controller can be placed outside the engine compartment, reducing the risk of sparks inside the compartment.

Additionally, make sure to follow other necessary precautions, such as removing the boat engine from the water, draining all water from the engine, and stabilizing the fuel. These steps will help prevent freezing and ensure the engine is protected from potential damage caused by freezing temperatures.

Frequently asked questions