How to Winterize a Sailboat and What You’ll Need + Checklist

Winter is coming, and it’s coming fast! Which means it’s time to prep the sails for the cold weather and ice. This process can be tedious and time consuming, but you’ll thank yourself in spring for winterizing your sailboat properly in the fall. But the question still remains:

How to winterize a sailboat and what you’ll need? You will need to prepare the engine and other mechanicals, clean the boat, and inspect it before putting it away for the winter. To do this, you will need the boat manual, cleaning supplies, antifreeze, boat cover, and sail repair supplies.

But before you start emptying tanks or pouring antifreeze into every open hole, let’s talk about the importance of winterizing, especially for sailboats.

Winterizing a Sailboat

To winterize a sailboat means to prepare the sailboat for the cold, harsh weather commonly associated with winter. This process is incredibly important for Northern climates with bodies of water that are more likely to freeze over; however, this practice can, for the most part, still be followed by those of us lucky enough to coast the warm Southern waters.

Winterizing a boat will protect it from damages caused by fluids that could freeze, blemishes that have gone without repair, and creatures seeking a warm home in the cool months.

Specifically for a sailboat, the process of winterizing can be essential in protecting the dacron, nylon, or whatever material the sail is made out of from rodents and UV damage.

How to Winterize a Sailboat

There are a lot of steps to properly preparing your sailboat for the next spring season. Although it might seem like a lot, each one is very important to ensure smooth sailing after winter waters thaw.

The process of winterizing a sailboat is to: prepare the tank, clean the engine, drain fuels, add antifreeze, replace the batteries, clean the boat, inspect the boat and sails for damages, repair and restore the sails, empty the head, arrange the cabin, and apply a cover.

1. Preparing the Tank

Depending on what type of tank or engine, your sailboat has will determine the best method for winterizing it. This is due to the design of each tank and how it processes fuel.

If you have a diesel engine, you’ll need to do the following:

  • Add stabilizer– This will prevent sludging and sediment formation, clean and lubricate fuel injectors, improve performance, and help to remove any water that microbes and algae require for growth.
  • Fill tank– You’ll want to fill the fuel tank to complete capacity with your desired diesel gas.
  • Replace Fuel Filters– All of the fuel filters will need to be completely replaced in the diesel engine. This is because its job is to catch particles and debris that would otherwise end up in the diesel tank. If the fuel filter gets dirty, clogged, or damaged, there’s no guarantee that only the diesel fuel will end up in the tank.
  • Drain Water Separator- As with the fuel filters, you’ll want to drain the water separator. This will protect the diesel tank from any introduction of microbes or algae.
  • Run Engine for 15 minutes– The engine can be run for longer than this, but it needs a minimum of 15 minutes in order to let the stabilized fuel flow through the system.

If you have a gasoline tank, you’ll need to do the following:

  • Run Fuel Off- Whether you choose to take the sailboat out for a long while or invest in a fuel hose, you’ll need to completely empty the gasoline tank. This will protect the physical tank from erosion due to absorbing moisture from the ethanol of leftover gas.
  • Leave the Tank Empty- There’s a lot of debate over whether or not to leave the tank empty over the winter, or replace all the fuel. To avoid the erosion, it is best to leave the tank empty. However, if condensation in the tank is a worry, check with your sailboat’s manual on how to remove the gasoline tank completely and store it in a dry, air-proof, stable environment.

If you have an inboard motor, you will need to do the following:

  • Follow Prior Steps- Depending on whether you have a diesel or gas tank, you’ll need to properly handle the fuel.
    • Diesel tank- leave fuel in and add fuel stabilizer
    • Gas tank- remove fuel from tank completely
  • Apply Antifreeze– We’ll go over more about antifreeze, but the important part of the sailboat that needs it is the engine.
    • If you have a sterndrive (inboard engine with an outboard drive system), you’ll need to drain the lines by storing the sterndrive in a down position before adding antifreeze.

If you have an outboard motor, you will need to do the following:

  • Follow Prior Steps- Depending on whether you have a diesel or gas tank, you’ll need to properly handle the fuel.
    • Diesel tank- leave fuel in and add fuel stabilizer
    • Gas tank- remove fuel from tank completely
  • Drain Motor- Because of the temperatures dropping, you’ll want to drain the motor entirely of any water. This can be done by dropping the outboard motor after leaving the ramp.

2. Preparing the Engine

No matter which tank or motor your sailboat may have, the engine can be winterized in the same fashion for all. It should be noted that these are suggestions to prolong the engine’s life and prepare the sailboat for spring sailing.


As stated before, antifreeze should be added to the engine in order to protect it from damage due to ice or frost.

  1. Fill a five-gallon bucket with antifreeze. A non-toxic antifreeze is suggested.
  2. Close the intake seacock.
  3. Transfer the hose to the bucket.
  4. Allow the exhaust to discharge the antifreeze.
    1. You’ll know when it’s done because the bucket will be nearly dry.
  5. Fog the carburetor (device that mixes air and fuel for internal combustion engines in the proper air–fuel ratio for combustion) with fogging oil.

Fogging Oil

Spray light amounts of fogging oil directly into the engine while it’s still warm. This will help to displace any moisture and protect the engine. It will also prevent scuffing during start-up after prolonged engine storage.

No matter the type of engine or horsepower, there will be white smoke that emanates from spraying the engine with the fogging oils.

Re-secure Seacock

Once the antifreeze bucket is empty, turn off the engine and re-secure the hose to the seacock. The instructions on how to reassemble the seacock should be in your boat manual.

If you do not wish to go through this process, you can also remove all the spark plugs and spray fogging oils straight into the engine’s combustion chamber. Note, there may still be white smoke.

Restart the Engine

Now, you can restart the engine. You’ll want to keep it at an idle state in order to let the engine reach regular temperatures on its own.

Do not over-cool the engine. Rather, let it cool off gradually over time.

Run the engine

Allow the engine to run for a minimum of 15 minutes. This is to give the fuel stabilizer enough time to enter the fuel system.

An oil stabilizer may also be added to the engine, but it’s not necessary.

3. Draining and Antifreeze

As mentioned throughout, draining the sailboat’s motor and adding antifreeze are two of the most important steps in order to winterize a sailboat. This process will protect the motor and tank from damage caused by frozen water left from the previous season.

  • Draining– You should completely drain the outboard motor as you are leaving the ramp. No water should be left in or around the motor as it will lead to cracking, which can keep you from sailing in the spring.
  • Antifreeze– As mentioned before, antifreeze should be added directly to the engine. It’s an extra precaution against frost damage and could save the life of your engine and sailboat.

4. Check the Batteries

This step is key to ensuring the lifetime of the boat’s batteries. If they’re left over the winter, you not only risk battery acid leakage but also erosion of the battery itself.

  • Remove the Batteries- The batteries should be removed completely from the sailboat.
  • Check Connections- As the batteries are out, check the electrical connections on bard. Are there any loose wires? Does anything look frayed or worn down?
    • It’s in your best interest to remove any and all the electronics from the sailboat during winter.
  • Recharge Batteries- The batteries should be recharged once every month. This will keep them prepared for the spring sailing season.

5. Clean the Sailboat

A clean sailboat is a happy sailboat. It may seem like waiting until spring to clean the boat would be the better option, but cleaning the sailboat before winter will help ensure no dust or debris is interfering with the motor. Plus, it’s one less thing keeping you from the open waters when everything defrosts!

Because sails can be so fragile, the following method is recommended:

  • Cleaning Area- Make room for where the sail is actually going to be placed while cleaning. You’ll need somewhere large, flat and as clean as possible.
  • Unfold the Sail- Whether if it was stored away or attached to the mast, you need to completely unfold the sail in the cleaning area.
    • Try not to have any wrinkles or folds when laying it out.
  • Cleaning the Sail- This will have to be done by hand, so leave the pressure-washer at home.
    • Dilute a bottle of mild liquid detergent in a large bucket of water.
    • Using a sponge, lightly scrub the sail.
    • Rinse thoroughly with fresh, warm water.
    • Repeat these steps for both sides of the sail.
    • Let it air dry completely in a shaded area.
      • This will reduce the risk of mold and mildew.
  • Refold– Refold the sail and stow it away properly in a dry environment.

6. Inspecting for Repairs

Inspecting for repairs is a key element in winterizing a sailboat. Any issues that are left unattended for long periods of time will only weaken the system. It’s best to address any issues during winterization before the bitter cold adds anymore complications.

Exhaust System

You’ll want to check the exhaust system for any signs of corrosion. This can be in the form of rust, cracks, or buildup.

  • Dissemble the exhaust system from the water lift muffler in order to get the best inspection.
  • Check to make sure the raw water injection hose hasn’t become obstructed.

Hoses and Hose Clamps

Because hoses carry the most amount of water and liquids through them, they are the first to become damaged by freezing temperatures.

Check for any cracks, shreds, or rust. If there is any sign of damage, replace them now!


Any type of crack, no matter how small, runs the risk of expansion with the ever-flowing temperatures and extra moisture in the air.

  • If there are any openings, seal them. The easiest solution to this is to use tape of any kind.
  • Double-check both your air inlet and exhaust outlets.


This is the best time to check your engine for any fuel filter leaks.

With the sailboat still in the water, start the engine and let it run. If there is a leak, check with your boat manual for the best solution. Otherwise, replace the installed filter.


Since everything has been cleaned, this is the opportunity to inspect the smaller devices on the sailboat.

Dock lines, flotation devices, flares, fire extinguishers, first-aid kits, and any other equipment on the boat should be inspected and replaced as need be.

7. Repair and store sails

The most essential part of any sailboat would be the sails. Due to their fragile materials, repairs to the sails should be done frequently throughout the season. For winterizing a sailboat, this becomes crucial for extending the lifetime of your sails.

Clean the sails

The sails should be cleaned after every use of them, so it makes sense that part of winterizing is to clean them once more.

  • Use clean water with a light, mild detergent.
  • A sponge is the best tool to hand wash with, but a brush can be used for stubborn spots. If you are using a brush, do not brush hard!
  • Make sure to keep the sails out of direct sunlight when drying. UV rays are harmful to Dacron and nylon.
  • If possible, dry them in a shaded spot or a garage.

Repair the Sails

You’ll want to thoroughly check the sails for any signs of damage. Even something as small as a tear could lead to a ruined sail.

Hand sewing any minor blemishes can get the job done, but the best method is to hire a professional sails repairman.

Storing the Sails

The Dacron material in sailcloth can attract mice and other rodents. To avoid holes in the sails, storing the sails properly becomes a must.

  • You can suspend the sail bags from a height. This should keep the rodents from being able to reach the sails.
  • You can also sprinkle mothballs inside the sail bag. For the best results, combine these two methods.

To read more on how to store your sails in winter please read our useful guide here.

8. Empty the Head

Although it may not be everyone’s favorite thing to do, the head (or toilet) will need to be drained and flushed out as part of the winterization process. After all, you don’t want to have to wait until spring to find out the head froze!

  1. Pump out the holding tank
  2. Add fresh water to the bowl
  3. Flush several times
  4. Close the water intake seacock,
  5. Remove the hose
  6. Pump the head full of antifreeze
  7. Put some of the antifreeze into the holding tank.
  8. Replace the hose
  9. Leave the seacock closed

9. Arrange the Cabin

Since you’ll be away from the sailboat for an entire season, now’s your chance to arrange the cabin and make sure everything is in order come spring.

If your boat has an inboard stove, you’ll want to make sure the propane bottles are completely closed. Also, remove any excess propane in the pipes by lighting the stove after closing off the propane bottles. Seal the end of the propane line and make sure there are no leaks. Remove the propane from the boat.

If your boat has any cushions, keep them nice by pulling them all out, tilting them upwards, and unzipping them so air can flow in and out.

If your sailboat has compartments, open them all along with any doors and hatches. This will increase the air flow and keep the boat from getting that musty smell.

If windows need to be stacked, place a bed sheet between each one to protect them from any damage caused by bumping, scraping, or any other outside force.

To protect your sailboat from rodents, sprinkle some mothballs around the cabin and remove all food.

10. Storing the Sailboat

As the weather begins to drop into low figures, storing the sailboat properly becomes critical to help ensure no damages occur over the months. There are two important factors that will help store the sailboat properly and should be done as part of the winterization process.

  • Climate control The sailboat and sail bags will both need to be stored in a climate controllable environment. The easiest method for this is to store it in your garage.
    • You’ll want to keep the environment dry and warm.
    • It wouldn’t be a terrible idea to invest in a backup generator for the temperature control of the garage.
  • Cover– A cover is a large canvas that will, no surprise, cover the entire sailboat. It is a necessity regardless of what environment you may choose to store the sailboat.
    • To help prevent rodents and bugs from making a home in the cover, you can use shrink-wrap before placing the cover on.
      • Note: be sure to use an anti-chafe material between the shrink-wrap and cover for easier removal in spring.
    • The best cover to use would be a customized one.

And speaking of covers…

How to Cover a Sailboat for Winter

Because covers are so essential to the protection of the sailboat, it’s very important that the cover be placed properly. Luckily, the people at CoverQuest have got you, well, covered!

  1. Place the bow end of the rolled cover on or near the bow of your boat and unroll towards the stern or back, positioning it down the center of the boat as you unroll.
    • PRO TIP: Can’t tell which end is which? Many boat covers have the tag sewn into the stern end of the cover.
  2. Slip the front of the cover over the bow and pull the cover open to the sides as you work towards the back of the boat.
  3. If using support poles (optional for most covers), position the poles under your cover prior to completely covering the boat.
    • Also add any padding needed for the windshields, trolling motors, depth finders, etc.
  4. Adjust cover fit by pulling cover tight to eliminate sagging areas.
    • These areas may collect standing water or snow and shorten the life of your cover.
  5. The braided tie-down rope provided can be used to secure the cover to the boat for storage only.
    • Cut the rope to the desired lengths, and using the reinforced tie-down loops, secure the cover to your trailer.
      • When trailering, always use heavy-duty tie-downs, sold separately.
  6. Remove the boat cover by folding to the center from both sides and rolling the cover from back to front. This will make it easier to repeat steps 1 thru 5 when covering your boat again.
    • Important: To avoid mold and mildew allow the cover to dry thoroughly before folding for storage.

What You’ll Need a Checklist

Because there are so many steps involved in winterizing a sailboat, here is a comprehensive checklist of all the supplies necessary for a smooth winterizing of your sailboat.

  • Boat manual
    • Because there might be specifications for how to best prepare for the winter, it is highly recommended that you read over your sailboat’s manual.
    • You will also need the manual as a guide for removing any parts such as the battery, spark plugs, etc.
  • Cleaning supplies
    • Multi-surface cleaner
    • Baby wipes
    • Surface cleaner
      • Specific for your sailboat’s cushions, tables, and other furniture
    • Sponge
    • Two buckets
    • Mild liquid detergent
      • For cleaning the sails
    • Feather duster
    • Broom and dust pan
    • Mop
  • Fuel Tank
    • Fuel tank receptacle
      • For emptying the gas tank
    • Stabilizer
    • Antifreeze
    • Fogging oil
    • Fuel hose
  • Cover
    • Shrink-wrap
    • Anti-chafe material
  • Repair supplies
    • Needles
    • Patches
    • Tape

Is it Necessary to Winterize a Sailboat?

There’s a lot to remember when it comes to winterizing a sailboat. It may seem like the whole process isn’t worth the hassle just to undo it all for spring. However, if proper winterization of a sailboat isn’t done, you risk the following dilemmas:

  1. Water Damage– Fresh water expands in volume by about nine percent when it freezes and can push outwards with a force of tens of thousands of pounds per square inch. That expansion can crack an engine block, damage fiberglass, split hoses, or destroy a refrigeration system overnight
  2. Sinking– If the sailboat is left in the cold waters over all those months, it risks sinking from possible damage done to the small underwater fitting from being exposed to the freezing and thawing of the ice.
  3. Storm damage– Winter brings with it a multitude of wicked storms. These storms can be extra damaging to sailboats as the nylon material is so fragile.
    1. High winds– With the storms, high winds can cause a lot of damage to not only the sails but the boat itself. These high winds can throw debris and other projectiles around.
    2. Torrential rains– The storms can also bring heavier rain droplets that can end up freezing onto the cover, or worse, directly to the boat. The rain also runs the risk of finding itself inside an unaccounted for crack and expanding- causing even greater damage.
  4. Rise and fall in water level- As the ice thaws and refreezes, the literal overnight change in water level can interrupt the sailboats buoyancy.
  5. Blisters– The hull needs a chance to dry out for several months in order to avoid developing blisters. Without proper winterizing, the sailboat’s hull suffers the consequences. Thus, so do you over the lost years of your sailboat.
  6. Theft- One of the most overlooked consequences of not winterizing your sailboat: theft. If you leave your sailboat in the waters and don’t properly care for it, people may begin to think that it’s been abandoned. Or worse, an easy target.

Preparing a sailboat for the spring season by winterization may seem like a chore with a multitude of steps. However, it is a crucial part of owning a sailboat or any boat for that matter. It’s necessary to follow this guide to ensure the maintenance of your sailboat is being kept up on and for a smoother sailing season in spring.

So, grab your first mate (and some pizza), bring all the supplies listed in the checklist, and try to take pride in the whole winterization process. After all, you might be packing away the sails for now, but it’s done knowing in a few months it’ll be smooth sailing.


I am the owner of sailoradvice. I live in Birmingham, UK and love to sail with my wife and three boys throughout the year.

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