Keeping a boat motor from freezing is important for preventing engine cracking and general boat motor damage.
Any fresh water in a boat motor will freeze at 32°F (0°C) or lower. Any salt water in a boat motor will freeze at 28.4°F (-2°C) or lower. Therefore, a boat motor can freeze in temperatures of 32°F (0°C) or lower. Cracks can form in the boat engine in temperatures of 32°F (0°C) or lower if the boat motor is exposed to this cold temperature for over 90 minutes.
There are 6 steps to prevent a boat motor from freezing.
To keep a boat motor from freezing:
- Remove the boat engine from the water
- Drain the boat motor from all the water
- Stabilize the fuel
- Change the gear lube oil
- Spray carburetor inlets & spark plug holes
- Cover the engine with a heated engine cover blanket
These boat engine freezing prevention steps can be applied to both an outboard motor and an inboard motor whether it's a two-stroke or four-stroke engine. A boat owner should check their boat motor owner's manual for specific information too.
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1. Remove The Boat Motor From The Water
The first step in keeping a boat motor from freezing is to remove the boat motor from the water.
Removing a boat motor from the water applies to outboard motors as inboard motors are already out of the seawater.
To remove a boat motor from the water:
- Bring a vehicle with a trailer to a boat ramp area and back the trailer down the boat ramp
- Move the boat from the seawater to the boat ramp and place the boat on the trailer
- Secure the boat to the towing trailer and ensure it is tied down properly
- Haul the boat out of the water with the vehicle
- Move the vehicle with the boat to a flat area where it can be worked on
Removing the boat from the water to work on the boat engine should take approximately 15 minutes to complete.
An outboard motor will need to be out of the seawater to prevent the motor from freezing.
2. Drain The Boat Motor From All The Water
The second step in keeping a boat motor from freezing is to drain the boat engine and the engine bay from all water including freshwater and salt water.
To drain the boat motor from all water:
- Trim the outboard motor to its maximum angle, typically 65 degrees
- Let all the trapped water be released onto the ground
- Wipe around the engine and engine bay with a sponge to release any trapped water
- Wipe around any flat horizontal surfaces around the engine where water may be trapped
Draining water from the boat motor takes approximately 5 minutes to complete. If the water is not drained, it can freeze and cause cracks to emerge on the engine's lower unit.
3. Stabilize The Fuel
The third step in keeping a boat motor from freezing is to stabilize the fuel.
To stabilize the fuel:
- Fill the fuel tank with fresh fuel until it's 99% full. Leave just enough space to put the fuel stabilizer in the fuel tank
- Pour fuel stabilizer into the fuel tank. 1 oz. of fuel stabilizer treats 2.5 gallons of fuel
- Start the boat motor and let it run idle at approximately 1,000 rpm for 5 minutes until the fuel stabilizer mixes into the entire fuel system
- Turn off the boat motor
Stabilizing the fuel will prevent the fuel from oxidizing and forming a pasty gum-like substance in the fuel tank and fuel lines. It prevents corrosion of the fuel tank too.
Stabilizing the fuel takes 7 minutes in total to complete.
4. Change The Gear Lube Oil
The fourth step in keeping a boat motor from freezing is to change the boat's gear lube.
To change the boat's gear lube oil:
- Put the engine into an upright position to allow the free flow of gear lube oil out of the tank
- Place an oil pan below the motor on the ground to store the gear lube oil waste
- Unscrew the lower and upper gear lube tank screws using a screwdriver. The gear lube tank is located in the lower unit of the motor near the propeller of an outboard motor
- Allow the old gear lube oil to flow out of the gear lube tank. If it is a milky yellow color, this is a sign that water has gotten into the gear lube tank. Draining the old gear lube oil from the tank takes approximately 12 minutes to do
- Ensure the gear lube oil tank is completely empty
- Connect a gear lube pump to the lower screw hole on the gear lube tank
- Pump fresh gear lube oil into the bottom screw hole until it flows out of the top gear lube hole. Filling the gear lube tank with fresh gear lube oil takes approximately 5 minutes
- Screw the two holes back up
Changing the gear lube is required to ensure there is no water in the gear lube tank that can freeze as temperatures drop to 32°F (0°C) or lower.
Any water in the gear lube tank can freeze and expand causing damage to the lower unit of the boat motor.
Changing the gear lube oil takes 20 minutes to complete.
5. Spray The Carburetor Inlets & Spark Plug Holes
The fifth step in keeping a boat motor from freezing is to spray the carburetor inlets and spark plug holes with a marine fogging spray. This is also known as fogging the motor.
To spray the carburetor inlets & spark plug holes:
- Remove the engine cover from the engine
- Start up the boat motor and let it run idle at approximately 1,000 rpm
- Spray marine engine fogging oil into the carburetors until the engine stalls
- Remove the spark plugs
- Spray 1 oz. of fogging oil into each spark plug hole
- Crank the engine for 30 seconds
- Spray the spark plug tips
- Reapply the spark plugs and engine cover
Spraying the spark plugs and carburetors takes approximately 10 minutes to complete.
Only use a marine-grade fogging spray. Spraying the spark plug holes and carburetors will prevent corrosion and help stop the boat motor from freezing.
6. Cover The Engine With A Heated Engine Cover Blanket
The sixth step in keeping a boat motor from freezing is to cover the engine with a heated engine cover blanket.
To cover the engine with a heated engine cover:
- Get a heated engine cover blanket that fits your specific boat motor
- Wrap the blanket around the engine
- Ensure there are no uncovered areas
Covering the engine with a heated engine cover blanket takes 2 minutes to complete.
Covering the engine with a heated boat engine cover will keep the motor from freezing and protect the boat motor from bad weather.
Products Needed To Keep A Boat Motor From Freezing
The products needed to prevent a boat motor from freezing are:
- Fuel Stabilizer
- Fuel
- Marine-Grade Fogging Spray
- Oil Waste Pan
- Gear Lube Pump
- Outboard Motor Cover Heater
- Gear Lube Oil
- Marine Anti-Freeze Spray
- Screwdriver
Keeping A Boat Motor From Freezing Checklist
Below is a checklist for keeping a boat motor from freezing i.e. winterizing a boat motor.
Frequently Asked Questions About Keeping A Boat Motor From Freezing
Below are the most commonly asked questions about keeping a boat motor from freezing.
Can An Outboard Motor Freeze?
Yes, an outboard motor can freeze in temperatures of 32°F (0°C) or lower.
Can An Inboard Motor Freeze?
Yes, an inboard motor can freeze in temperatures of 32°F (0°C) or lower.
What Are The Benefits Of Keeping A Boat Motor From Freezing?
The benefits of keeping a boat motor from freezing are:
- Protects the engine: Freezing temperatures can cause damage to the engine by cracking or warping the cylinder walls, pistons, and other internal components. Preventing freezing can help protect these critical parts and prolong the life of the engine
- Reduces repair costs: If a boat motor freezes and sustains damage, the repair costs can be significant. Preventing freezing can help keep these costs down
- Ensures reliable performance: A frozen motor may not start or run properly, which can be a major inconvenience and even a safety hazard. Preventing freezing can help ensure that the motor is always ready to go when you are
- Enhances safety: Frozen motors can cause accidents and injuries, and preventing freezing can help keep you and others safe
- Maintain resale value: A well-maintained motor that has not been damaged by freezing will typically have a higher resale value than one that has
- Peace of mind: Knowing that your boat motor is protected from freezing can give you peace of mind and allow you to enjoy your time on the water without worrying about potential problems
What Is The Fastest Way To Keep A Boat Motor From Freezing?
The fastest way to keep a boat motor from freezing is to cover the engine with a heated engine cover blanket. This will take approximately 3 minutes to complete.
What Is The Slowest Way To Keep A Boat Motor From Freezing?
The slowest way to keep a boat motor from freezing is to completely remove the boat motor from the boat, stabilize the fuel, change the gear lube oil, change the fuel and air filters, fog the engine with fogging spray and cover the engine with a covered heater. Doing this would take approximately 90 minutes to complete.
What Are The Differences Between Keeping An Outboard Motor From Freezing Versus An Inboard Motor?
The differences between keeping an outboard motor from freezing versus an inboard motor are:
- Easier to regulate temperatures on an inboard motor: Compared to an outboard motor, preventing an inboard motor from freezing is easier as regulating the temperature inside a boat is easier than trying to regulate the temperature of a boat motor in the water
- Inboard engine is faster to keep from freezing: Compared to an outboard motor, preventing an inboard motor from freezing is faster to complete as it takes 10 minutes to winterize an inboard motor compared to 20 minutes for an outboard motor
- More marine anti-freeze product is used on an inboard: As parts on an inboard engine are harder to reach, more anti-freeze product will be used on an inboard motor compared to an outboard motor
When Is The Best Time To Winterize A Boat Engine?
The best time to winterize a boat motor and prevent it from freezing is before the temperature drops to 32°F (0°C) or before storing the boat for the winter season.
Will A Boat Motor Get Damaged In Freezing Temperatures?
Yes, a boat motor can get damaged in temperatures of 32°F (0°C) or lower if it is exposed to cold weather for over 90 minutes. Cracks and damage can form on all engine parts from pumps, filters, seacocks, seals, etc.
What Should You Avoid When Keeping A Boat Motor From Freezing?
When keeping a boat motor from freezing, you should avoid removing fuel from the fuel tank and avoid keeping the boat motor (outboard) in the water.
How Much Does It Cost To Keep A Boat Motor From Freezing?
The cost to keep a boat motor from freezing is approximately $150. However, this price can vary depending on the products purchased to prevent the boat motor from freezing.
How Long Does It Take To Prevent A Boat Motor From Freezing?
Winterizing the boat motor and preventing it from freezing takes 1 hour to complete.
How Do You Keep A Boat Motor Warm?
To keep a boat motor warm, use a boat motor cover heater and wrap it around the engine, use a bilge heater near the motor to keep it warm, or simply wrap a waterproof electric blanket around the engine.
This will keep the marine engine warm and help to prevent it from freezing.
What Happens If A Boat Motor Freezes?
If a boat motor freezes, cracks can form in the engine block, lower unit, pumps, fuel lines, or cooling system. A frozen boat motor can prevent the engine from running too.