What Does Winterizing a Boat Mean? (Answered)

The term “winterizing a boat” is something you hear about often, mainly if you live in an area of the country where it gets below freezing in the winter. For new boat owners, or potential new boat owners, that term may sound very foreign to you. You don’t have to winterize a car, so why do you have to winterize a boat? Better yet, what does winterizing a boat mean?

I don’t claim to be an expert on boats or engines, but I have owned a couple of boats and have dealt with winterizing them. So I decided to pass on what knowledge I have about the subject. I also did some additional research to answer some commonly asked questions about the process of winterizing a boat, and to clarify a pretty simple process.

Let’s take a look, and demystify exactly what winterizing a boat is!

What does winterizing a boat mean?

Winterizing a boat simply refers to performing certain preventative maintenance each year to ensure that your boat is ready for the next boating season and does not get damaged in any way when it gets below freezing. So while there are quite a few steps involved in winterizing a boat, many of which are optional or not necessarily done every year, the main focus is the engine, fuel systems, and anything that is potentially holding water.  

What does winterizing a boat include?

As mentioned, there are several things that you have to do in order to fully winterize your boat for the off-season. What exactly must be done to your own boat varies, but below are the main things involved in winterizing a boat. The first on the list should be done each year, while others should be done if necessary.

Primary checklist when winterizing a boat:

  • Drain the engine block, manifold, circulating pump and coolers of water to prevent freezing and cracking
  • Fill the engine block, manifold and circulating pump with antifreeze
  • Burn as much fuel as possible then add fuel stabilizer to help prevent phase separation
  • Fog the engine cylinders
  • Spray entire engine with anticorrosion treatment
  • Clean fuel screens and replace fuel filter
  • Change oil and oil filter
  • Change the gear case lube
  • Be sure all water is removed from any additional systems and reservoirs
  • Remove the drain plug(s)
  • Cover and store your boat for the winter

List of other items that you may want to check or have checked:

  • Fuel line and bulb
  • Plugs, wires, rotor, cap
  • Belts, adjust tension
  • All hoses
  • Shift/throttle cables and settings
  • Lube shift/throttle cables and linkages
  • Flush cooling system
  • Check gimbal bearing
  • Grease U-joints and gimbals
  • Lube engine coupler splines
  • Sacrificial anodes
  • Steering and power trim fluids
  • Propeller/hub and prop shaft
  • Lube splines
  • Water pump impeller
  • Spray electrical connections with moisture repellent
  • Remove battery and recharge if necessary
Don't forget to flush your engine!
This Do-It-Yourself winterizing kit allows flushing and preparation of boat engines for winter storage with five gallons of marine antifreeze.

Can I winterize my boat myself?

Absolutely! Winterizing a boat is not difficult, but if you’ve never done it before expect to spend some time watching YouTube videos and doing a bunch of research. As well as getting your hands dirty. So it could be rather time-consuming for someone who has never done it before and not great around engines.

Some of us just like driving our boats and enjoying the water, the self-maintenance part of boat ownership isn’t for everyone.

What do I need to buy to winterize my boat?

Again, this may vary from engine to engine. What you need to winterize an outboard engine may be slightly different from what you need to winterize a inboard/outboard, or sterndrive.

But here are the essentials and basic things you may need to buy in order to successfully winterize your boat.

How much does winterizing a boat cost?

Again, it depends on the type of engine and also if you already of the things required on hand. If you’re going to do it yourself, probably under $100 in materials and a few hours of your time. However if you hire someone to do it might be more like $300 or $400 dollars to winterize your boat.

How long does it take to winterize a boat?

Another difficult question to answer because of how many variable there are, but generally winterizing a boat shouldn’t take more than 2-3 hours max. Once you are used to your own boat and have all of the supplies need on-hand, you may be able to winterize your boat much quicker.

Should I hire a professional to winterize my boat?

As I mentioned above, I think that most people certainly have the capability to winterize their own boat. It doesn’t require any special skills, but to do it correctly it could take a good bit of your time. A lot of times when it comes to things like this that require me to learn a new skill, I ask myself a couple of questions:

  • Do I want to learn how to do it?
  • Is learning how to do it worth the money I’ll save in the long run?
  • Is the amount of time it will take me to do it myself more valuable than just hiring someone else to do it?

Let’s say you value your personal time at $50/hour, and you figure it could take you 8 hours to totally winterize your boat. For this example we’ll also say that a mechanic will winterize your boat for $300. By that logic, doing it yourself is $100 more expensive. However you’d learn a valuable skill and know how to do it quicker for next season. It’s a tough choice.

I say if you aren’t mechanically inclined and have the extra money to spend, just hire a professional and be done with it. However if you are looking to save money where you can and are good with your hands, just do it yourself.

Knowing when to winterize a boat

We’ve covered the steps involved in winterizing your boat, but how do you know when it’s time to winterize your boat?

There’s not an exact time of the year to winterize your boat, that changes from year to year based on the weather. The main thing we are avoiding when winterizing our engine is avoiding freezing temperatures before we do so.

At what temp should you winterize your boat?

There’s really no hard and fast rule, but generally it’s recommended that you drain your block and winterize your boat when the temperature is starting to get close to or below freezing at night. Better yet you can do it as soon as you are finished taking it out for the season, which will probably be well before the first cold snap where it gets below freezing.

However there are many factors at play here.

Engines of boats stored in the water all winter don’t get as cold at night because the water temp takes a while to cool down, so that gives you a little extra wiggle room perhaps. Also, a quick cold snap of below freezing for just one night isn’t going to be enough to crack your block, but it’s a red flag that you need to go ahead and get your boat’s engine ready for winter.

In the end it’s a judgement call that you have to make as to when you should winterize your boat, I always err on the side of caution and do it just a little bit earlier than I probably have to.

Is it too late to winterize my boat?

That depends, if not winterizing your boat has already done irreparable damage to your engine, then probably. However if it hasn’t really been below freezing yet at night, or maybe only a few times and only for a few hours at a time, then you’re fine to still winterize your boat.

Better late than never in most cases.

Do I need to de-winterize my boat in the spring?

In a sense yes, once the weather has warmed up. However if you did a comprehensive winterization at the end of last season then you just need to do a check of all your systems and engine components to make sure everything is in or order, then you can hit the water.

A few of the main things you should check when getting your boat out for the first time of the season are:

  • Change the oil (if you didn’t when you winterized)
  • Add antifreeze mixture if needed
  • Check fuel lines and belts
  • Check the battery and electronics
  • Trailer tires (if you trailer your boat)
  • Check your safety gear and head to the lake!

Is winterizing a boat necessary?

That depends on a number of things.

Does it get below freezing for extended periods where you live in the winter? If the answer is yes then you probably need to winterize your boat. However if you live in a region where it’s rare to even get into the 40s in the winter then you won’t need to take all of the steps that someone would who lives somewhere that has harsh winters.

If you are someone who lives somewhere that has hard freezes, then you absolutely need to winterize your boat each and every season.

What happens if you don’t winterize your boat?

About the worst thing can happen is that the water in your engine freezes, expands, and cracks your engine block. This type of damage is catastrophic to a boat engine. So, consider any other system components that also hold water and what would happen if they froze as well.

Dirty oil can cause corrosion, which may also cause problems and shorten the life of your engine. If you don’t stabilize your fuel it can lead to separation which also causes a host of problems including gumming and difficulty starting and running of the engine.

Not winterizing your boat doesn’t guarantee problems, but it greatly increases your chances of them. The absolute main concern though, is draining the water out that could freeze and crack your block.

Do I need to winterize my boat if I keep it in the garage?

It really depends on if your garage is temperature controlled like the rest of your house. If it isn’t then you absolutely do need to go through the motions of winterizing your boat, since it will reach freezing temperatures in the garage. If your garage is temperature controlled and stays warm all winter then there are still certain things you’ll still need to do to winterize your boat, but other things you can get away with skipping if you choose to.

Even if you store your boat in a temperature controlled garage or storage unit, you should still do certain things such as add fuel stabilizer, change your fuel filter, and change your oil. However I can understand that if you are paying for premium storage you may not want to pay the extra that it costs to winterize your boat.

So while you may not always “need to winterize” your boat when stored inside all winter, you might as well service the main components of your engine while it’s out of the water for the season.

Is it necessary to winterize your outboard motor?

Yes, it is necessary to winterize an outboard engine just like you need to winterize an inboard or inboard/outboard. Any engine that holds water in its components runs the risk of freezing and causing severe damage in cold weather. Aside from that, after the boating season is over is the best time to perform the other preventative maintenance that we’ve discussed.

Can you winterize a boat that won’t start?

You can probably do the bare minimum and drain the engine so it doesn’t freeze, but that’s really not enough. In order to properly winterize a boat engine you need to perform other tasks that do require the engine to start.

You’ll also need to protect the fuel and cylinders as well as the motor oil. When you change the motor oil the engine needs to be started so that the new engine oil can be properly circulated before fogging running it on the fuel/oil mixture.

How cold does it need to be to crack an engine block in a boat?

It’s probably going to take a hard freeze of around 20 degrees for an entire day to freeze a boat engine block that hasn’t been drained and winterized. That’s just an estimate, but a quick cold snap for a few hours won’t be enough.

How do I know if my boat engine has a cracked block?

The main signs of a cracked engine block are:

  • Water in the bilge
  • Engine overheating
  • Engine smoke
  • Antifreeze or water and engine oil are mixing
  • Overall poor engine performance

If you want to be sure, just take it to a shop and get your engine inspected and get a pressure test.

Can a cracked boat engine block be repaired?

Of course it can be repaired, though in many cases the real question is if it is worth being repaired. First off, your engine is shot and will require some major work so know that right off the bat. You are either going to need major repairs done, or a total engine swap.

Now if your boat only cost you $3k, then you may want to just consider finding another boat. It never hurts to get an estimate or to look around for used engines, but you could be looking at anywhere from $3k-$5k to repair an engine block. In many cases, especially with cheaper used boats, it may not be worth it to fix.

However if we’re talking about a $50k dollar boat that you just bought a couple of seasons ago then that’s a different story. To answer the question though, a cracked block can be replaced and the engine can be repaired. A cast iron engine block should never be welded, so in that sense it can’t be “repaired”.


I hope this article has helped to give you a high overview of what exactly is involved in winterizing a boat. If this is something you want to try and do yourself, then I suggest heading over to YouTube and searching up “how to winterize [insert your engine]”. You should get plenty of good results.

A step by step tutorial of how to winterize a boat is out of the scope of this article and is something you’ll need to track down based on the type of engine and boat you have. YouTube has some great tutorials for just about every type of boat and engine you can think of.

Written by OutdoorMotives

At outdoormotives.com we talk about all types of outdoor activities. We answer common questions and recommend the best products to help you enjoy the outdoors as much as possible.


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