How to Winterize a Boat: The Ultimate Guide

 Written by Carolyn Jackson

Once the summer months come to a close and the pumpkin spice everything starts to reappear, you will need to think about winterizing your boat for the season. There are a few steps every boat owner needs to take to ensure their boat remains in good condition while sitting unused for a few months. 


Key Takeaways:

  • Winterizing your boat is important regardless of the climate that you live in
  • You can winterize your boat yourself or pay a professional
  • The most important takeaway is to ensure there is no water or moisture in your boat throughout the winter months
  • Not properly winterizing and storing your boat can lead to costly repairs



How Do I Winterize My Boat?

No matter where you live, we would still recommend going through the process of winterizing your boat. Temperatures can drop into the freezing zone quickly and without much warning, which can lead to expensive and lasting damage to your boat. 


There are 5 easy steps to follow when you are ready to winterize your boat (or jet ski):

  1. Clean everything
  2. Prepare the engine 
  3. Winterizing the freshwater and wastewater systems
  4. Winterizing the cabin and interior
  5. Cover and store your boat 


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Can I Winterize My Boat Myself?

Yes! Winterizing your boat yourself should only take an afternoon and will save you hundreds of dollars. 


What is a Winterizing Kit?

If you’ve started researching winterizing your boat, you probably came across a “winterizing kit”. A winterizing kit is a compact supply of all the tools and supplies you would need to winterize a boat on your own. These kits include items like an antifreeze jug, tubing to pump out moisture, and antifreeze. 


Most kits are between $50 and $100 and can be purchased online. Here are some of the top kits available today: 

  1. Wholesale Marine Winterizing Kit
  2. West Marine Antifreeze Kit
  3. Defender Winterizing Kits


Can I Pay Someone Else to Winterize My Boat for Me?

Yes, you can. It is a little pricey though. You can expect to pay anywhere from $300-$600 for a mechanic to winterize your boat for you.


Do I Need to Winterize My Boat?

If you live in a warmer climate, you might not think you need to winterize your boat. Although it might be warmer, freezing temps can still happen and the damage is not worth the risk. 


Winterizing your boat is an extremely effective way to not only protect your boat from damage but also to maintain the boat to increase its lifespan. Winterizing will keep your boat clean and in great condition, which will positively impact resale or trade-in value when you decide to upgrade to a newer model. 


Additionally, the more work you do up-front in the fall to winterize your boat, the sooner you and your family can get on the water when the weather warms up again. 


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Steps for Winterizing Your Boat

Step 1: Clean Everything

The first step and one of the most important is to thoroughly clean the interior and exterior of your boat. 


Items You Will Need:

  • A hose
  • A power washer attachment
  • A bucket 
  • Some rags/towels
  • Bilge cleaner solution
  • Vinyl cleaner solution
  • Boat cleaner solution
  • Fiberglass wax


Start with the interior of the boat. Wash everything with the hose first to shake off any loose dust. Then, use the power washer attachment on the carpet or any hard plastic materials. Now use your vinyl cleaner on the seats and the boat cleaner on the floor and other areas, like tables or a cooler or the bimini. 


Thoroughly clean every surface area on the inside of the boat and then move to the outside. Use the power washing attachment and the boat cleaner solution to clear any scum, algae, and dirt from the exterior of the boat. 


If you have a fiberglass boat, now is the perfect time to polish the boat with a fiberglass wax coat. This will protect the boat from scuffs, scrapes, dirt, and algae buildup.


Step 2: Ready the Engine and Lower Unit

It is extremely important to winterize your engine at the end of the season. Any freeze damage to the engine will result in costly repairs.

Items You Will Need:

  • Fuel stabilizer
  • Fogging Oil
  • Boat-specific antifreeze (4-5 gallons)
  • Oil-changing pump
  • 4-cycle oil
  • Oil filter
  • Lower unit fluid


Here’s how to winterize your boat’s engine:


  1. Add a fuel stabilizer to top off the fuel tank
    1. Make sure the fuel tank is full before adding the stabilizer to reduce air in the tank so there is no moisture that can freeze when temperatures drop
  2. Flush the engine with antifreeze
    1. Fog the carburetor at this stop
  3. Change the oil in the engine
  4. If you have an outboard engine or sterndrive engine, change the lower unit fluid


Step 3: Preparing Freshwater and Wastewater Systems 

You need to extract all the water from the boat and replace it with antifreeze. Any water remaining in the boat throughout the winter months can freeze and expand, which can lead to cracks that are costly to repair. 


Items You Will Need

  • 6-12 Gallons of boat-specific antifreeze
  • A 5-gallon bucket


Winterizing the freshwater in your boat is an easy process. 

  1. Turn on the freshwater pump and open any freshwater faucets. Allow the faucets to run until the tank is dry 
  2. Turn the freshwater pump off
  3. Pour 4-6 gallons of antifreeze into the fresh water tank
  4. Close all faucets except for the hot water supply fixture furthest from the pump
  5. Turn the pump on and run that faucet so antifreeze runs through the entire system
    1. Turn the faucet off when you see antifreeze run out
  6. Repeat the last step for each freshwater faucet for both cold and hot water


How to winterize the wastewater system: 

  1. Pump the holding tank
  2. Remove the intake hose from the seacock and place it in a small bucket with antifreeze
  3. Circulate antifreeze through the entire system


Step 4: Prepare the Interior and Cabin

The most important step to remember is to remove any perishables or removable valuables from the cabin of the boat. Sitting boats can be a target for theft and you don’t want to have to replace expensive items. 


Open up any doors or cabinets to increase ventilation and place dehumidifiers, such as mildew gasbags or star brite crystals, in several locations throughout the interior.  


Pump out the bilge and put some antifreeze in the lines to flush them of any remaining water. 


Remove the batteries from the boat and take them home. Store them in a cool, dry place for the winter, but not on a concrete surface as this will drain the battery. Before removing the battery, make sure it is fully charged. 


Step 5: Cover and Store the Boat

The final step is to put a cover on the boat to protect it from the winter weather. A cover will prevent the boat from enduring freezing and thawing from the winter weather which can cause cracks, mildew, and leaks. A cover will keep your boat clean and prevent costly damage, getting you out on the water sooner. 


It is important to consider how you will store your boat over the winter as you do have a few options. 


  1. Store on a trailer or cradle on dry land
  2. Find a storage facility
  3. Store in the water


We recommend storing the boat on dry land either on a trailer or in a storage facility. Usually larger boats will need to secure a space in a storage facility, but smaller pontoons or ski boats can manage on a trailer as long as you have a safe place to leave the trailer for a few months. 


Even if you live in a milder climate, storing your boat in the water can lead to increased water retention, which can lead to decay, mildew, mold, and cracks in the hull or other areas of the boat. Make sure the trailer or cradle is stable and blocked off so it does not move. 


When storing your boat, store with the bow higher and remove the drain plugs so any water can escape. 


To Sum it Up

It might seem like a lot of work, but one afternoon can save you thousands of dollars in repairs. Any water that gets on your boat when its cold can freeze, which will expand and cause costly damage to pipes, the engine, and the boat itself. 


Another reason to winterize your boat is to keep the interior and exterior, plus all the fixtures and parts clean and in tip-top shape. This will ensure that your boat runs well in the spring and that its lifetime is as long as possible. 

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