How to keep a boat motor from freezing

You've landed on this page because you're looking for information on how to keep a boat motor from freezing.

Well, you've come to the right place.

As with everything negative in life, prevention is better than cure so attempting to protect against freeze damage and general cold weather is much better than discovering afterwards that you have an impaired boat motor.

So what are the steps to take?

In this article, we'll discuss both prevention and cure so if you're in the unfortunate situation of already having freeze damage, we will discuss what to do in that situation also.

In this article, we'll cover:

  • Will A Boat Motor Freeze
  • How Cold To Freeze A Boat Engine
  • How To Keep A Boat Motor From Freezing [Video Guides]
  • Do You Need To Put Anti Freeze In Boat Motor
  • How To Keep Your Boat Engine Warm In The Winter

Ensuring your boat motor won't freeze is very important especially when storing your boat in winter!

Right, let's dig into how to keep a boat motor from freezing. We'll go into both an outboard and inboard motor.

If you don't know what the difference is, don't worry, you can read the difference between an outboard and inboard motor and come back.

But suffice to say, the majority of readers will have an outboard motorboat, i.e. your standard speed boat, jet ski etc.

First up is the outboard motor below.


Following the steps below will help prevent your outboard motorboat engine from freezing during the winter months. These are considered best practices and crucial for your engines safety and durability.

You can also check out a videos below if you prefer. There are 3 videos as a step by step you can follow.

Protecting your boat motor is divided up into 4 steps which are all outlined below (with video instructions) so you can follow along one step at a time.

The very first step before getting into the nitty gritty is a simple one. First you want to drain water from the outboard motor.


  • Get the boat out of the water and on level ground
  • Trim the outboard motor all the way down. This will help push all the water out of the motor.
  • Let it sit in the downward position for a minute and let the water drain.
  • Rinse and repeat the exact same process again. (Put the motor back in a level position and trim it down again)


Once you've drained the water from your outboard motor, you'll want to stabilize the fuel.

This is as easy as mixing a fuel stabilizer into your fuel tank and letting the engine run for 10 - 15 minutes.

Here's a video on how to do just that:

When stabilizing the fuel, you'll need to buy a fuel stabilizer. It's cheap and can be bought on Amazon

winterizing boat


Once you've completed this step above, you can move onto the next step. In this, what'll you need to do is:

  • Remove Engine Cover
  • You'll next need to gain access to the inlets of the carburetor (air cleaner)
  • You'll need fogging oil to spray into the inlets of the carburetor . (this helps alleviate corrosion.
  • Start the engine and slowly spray the fogging oil into the inlets. This will cause the engine to bog down.
  • Slowly repeat this step until the engine dies. (this is normal)
  • Don't over-spray it at the beginning
  • Make sure the RPM of the engine is above neutral
  • After completing this step (and reattaching the carburetor inlet cover), you'll want to remove the spark plugs
  • Once removed, spray into the holes where the spark plugs are placed with the fogging oil spray.
  • Next put some paper towels over the spark plug holes and crank the engine over. (it won't start because there's no spark plugs)
  • As you crank the engine, this will help the fogging oil to circulate through the cylinders.
  • Once done, reinsert the spark plugs

Here's a video on how to do these steps:

And you can get the fogging spray at your local marina or on Amazon

keep boat engine from freezing


Okay, onto the final step to winterizing your boat motor and preventing it from freezing. In this step, you'll want to change the lower unit gear oil.  

Follow these steps and watch the video below on how to do this.

  • Move the motor into the upright position
  • Remove the lower and upper screws of the lower unit
  • Make sure you have somewhere to drain all the oil into
  • Let it drain for 20 - 25 minutes (we want to get as much cleared)
  • Once the oil has been drained from the lower unit, you'll need a gear lube pump and gear lube
  • Put the gear lube pump on the lower hole and pump the gear lube through it until the lube comes out of the upper screw hole.
  • Allow 10 minutes for the gear oil to settle.
  • Screw back on the upper and lower screws in the lower unit. (you'll need new seals which will cost you $1 - $2)

Here's the final video with the latest steps explained in the video.

As mentioned in the video and steps above, you'll need gear oil and a gear lube pump. You can purchase these at your local marina or online for around $20


Below are some additional tips for protecting your engine as well as best practices. Some are cheap to implement while others are more expensive.


As we've shown above, it's best to use anti freeze or some other sort of preventative measures to stop issues arising with your boat engine during colder climates.

However, as a word of caution, only use products approved to do the job and don't second guess this.

The last thing you want to do is put some dodgy 'do it yourself' type liquid through your engine only to destroy it so stick to the approved stuff (some examples are above)

If you can drain your boat motor from water effectively and store it appropriately, you'll not suffer from the damage caused by freezing and as so many find out the hard way, it can most definitely be costly.


There are many different ways to keep your boat engine warm and protected from harsh winter climates.

Here are some options available:


outboard motor engine cover

Browse online to find the best engine cover for your boat. Luckily, Amazon has them in different shapes and sizes. (make sure to get the right size for your boat)

Keeping your engine safe and functional doesn't have to be complicated.

You can simply purchase a heated outboard motor cover, like the one above and simply have it protect your engine.

You can find these type of covers in your local marina store usually. If you don't have roofed storage, these are particularly useful.

The types of covers can range from $50 -$200 depending on what you are looking for.

You can also get customized versions made specifically for your boat too which can also be a great way of protecting your motor.


This needs no explanation. If you can afford to have it stored in storage facilities, we'd highly recommend you do that

A simply google search for "storage units near me" should bring up your local options.


bilge heaters winter months

If you are concerned about water trapping in the engine block, you could get yourself an electric bilge heater.

These can range from $100 - $1,000 depending on size but the majority of our readers could pick one up for $150.

You can get one at your local marina store or Amazon for the latest prices.


image courtesy of multicaisses

This is an option to keep your boats motor safe and warm during winter months. If you want, you can simply dismantle the outboard motor from the boat and place it in a case.

This is not necessary in most cases but still something to consider for those in very harsh climates during the cooler months.


Now, not wanting to scare anyone but if you don't protect your boats in harsher climates. these are some of things you can look forward to:


lower unit freeze damage
image courtesy of boatUS

Freezing temperatures can cause cracks which can become much bigger problems down the line.

This is one of the biggest problems with boat engines being exposed to the elements. Look at the nasty crack in the image above, seems harmless but it will cause much bigger damage once back in the water.

This is what you want to prevent.


winterized boat
photo courtesy of BoatUS

Hopefully this doesn't happen to any of you but a failure to take proper care of your boat engine can result in the engine block cracking.

This can be a very costly thing to fix (sometimes in the thousands of dollars) so please do take proper care of your equipment.


how to keep a boat motor from freezing

A very popular question asked by a concerned boat owner, (mainly outboard motorboats) is Will A Boat Motor Freeze?

The simple answer is yes. If the temperature is low enough, it can freeze. Water, oil and other engine related lubrication coupled with freezing temperatures is the main culprit for freezing a boat motor.

There can also be an unseen build up (even small) of seawater which, if not treated, can freeze your boats motor.

So coming into colder climates, you'll obviously want to make sure your boat engine is winterized. Don't panic as it's not a big deal to do when done right and we'll discuss how to do this below.

But as mentioned from the outset, it's considered best practice to have your motor prepared for the colder climates rather than discover AFTER that you've damaged the motor.

How cold does it have to get to crack a boat engine block?

Temperatures of 25 degrees Fahrenheit (-3 degrees Celsius) can result in a boat engine block cracking if left unprotected. You'll also want to ensure there is no build up of dirt on the hull when taking it out of the water.

How Cold Does It Have To Be To Freeze A Boat Motor?

So when should you be concerned about freezing related issues? How cold does it have to be to freeze a boat engine? A boat motor will typically begin to freeze at 32 degrees Fahrenheit (0 degrees Celsius)

So if the weather forecast predicts temperatures to drop below freezing, you'll want to make plans to protect against any freeze damage.


It's always best practice to ensure your boat is prepped for harsher winter climates. With that in mind, follow along with the steps and video guides above.

For a total of about $50, you'll have your boat winterized and ready. However, it is still best to store your boat motor in a storage area sheltered from the elements.

If you can't store it somewhere indoors like a garage, use the example above to prep and then buy a heated boat cover to help.

As the damage from freezing temperatures shows, it's best to be safe rather than sorry. So with that in mind, we wish you all safe boating and hopefully you'll never sustain any boat damage from cooler climates.