How To Winterize A Boat?

How To Winterize A Boat?

Many people claim that fall is the best season for sailing in New England. While you are still enjoying sunny and warm fall days on the water, it is always a good idea to start thinking about boat winterization earlier in the season. If you live in a climate that does not allow year-round boating, these useful tips on how to winterize a boat would be a great asset to you.

Boat Winter Storage:

Keeping your boat indoors in a designated facility with climate control is the most preferred way of storing during the off-season. Unfortunately, due to the high costs and limited availability, this option is not always accessible for most boat owners. The second-best decision is to store the boat on land in order to avoid sinking and storm damage that could occur if stored in the water. Remember that boats stored ashore are more prone to sudden freeze damage when the temperatures drop. Therefore, they should be winterized much sooner in the season compared to the boats kept in the water. It is always best to use custom-made winter covers to protect your boat from precipitation and extend the life of your deck and coach roof.

Engine Winterization:

According to Boat U.S. Marine Insurance provider in the past ten years, more than three-quarters of freeze claims included cracks in the engine block or the exhaust manifolds caused by the water freezing in the engine or cooling system. Thus, getting the boats’ engine ready for the winter and doing it the right way should become your priority.

Inboards and stern-drives engine:

  • Drain the engine by removing the water-pump hose from the bottom of the water pump, so there is no water left inside. Water in the cooling chambers expands after freezing and can crack the engine block and manifold. Refer to the user’s manual to locate all petcocks. Outboards self-drain boat types do not require this step. If not done correctly, complete engine replacement might be needed as a result of the freeze damage.

Engine Cylinders:

  • Use aerosol fogging products to keep the rust and corrosion away from bearings, seals, and rotating surfaces. To do that attach ‘ear muffs’ and a garden hose to the engine, start it and inject fogging oil into the air intake using the electronic fuel injection system.

Engine Oil:

  • Change engine oil and oil filters at the end of the season to prevent corrosion and get rid of any excessive moisture. If not done in the fall, moisture can cause excessive wear to your engine, affect fuel economy and even cause engine failure. Some mechanics say it is better to change oil twice a year- at the end of the season and then back in spring to keep the engine in a good working condition.

Fuel Treatment:

An essential step of boat winterization is fuel treatment. Fuel treatment also called fuel stabilization, is done to avoid clogs caused by varnish deposits. For some boat models, the manufacturers give you the option to drain your fuel tank completely during the off-season months. Refer to your user’s manual for any instructions on how to empty the tank. If your boat requires fuel treatment, follow the procedure below:

  • Change fuel filters and checks for leaks while engine running.
  • Add stabilizer (PRI-G, Stabil, etc.), run the engine for at least 10 mins to let the stabilized fuel circulate in the system.
  • After filling the tank to 95% full, so there is enough space for expansion. Having the tank full will prevent gas from oxidizing and ethanol in the fuel will be less likely to absorb moist air and separate from gasoline.

Fresh Water System:

Fresh water system and all the plumbing fittings, pumps and marine heads are highly prone to cracks caused by water freezing into ice. Adding antifreeze will get your system ready for the cold weather and help you avoid costly repairs.

Fresh Water System Winterization Key Concepts

  • Drain the water from the water tank and hot water heater by opening all water outlet spigots
  • Connect in and out lines together in order to disconnect hot water heater from the rest of the system
  • Use non-toxic anti-freeze to pump it through the system, including a hot water heater. Turn on all faucets including faucets in the bathroom to let the anti-freeze get out of the system. Do this step for both hot and cold water lines.

Freshwater from Reverse Osmosis Desalinators

Onboard reverse osmosis desalinators are typically seen in commercial and defense applications, although there are serious boaters, particularly those who plan long voyages, that keep seawater desalinators onboard to reduce the number of trips back to shore.

It’s easy to forget about maintenance, but be warned. The membranes are meant to be used regularly, and a 4-to-6-month hiatus can foul the membranes, which renders the desalinator unusable. The cost to replace membranes is roughly double the cost of pickling and storing RO membranes over the winter.


For smaller boats, it is always better a better idea to remove batteries and store them at home until the next season. If you decide to keep the battery onboard follow these simple steps:

  • Top wet-cherbell batteries with electrolyte.
  • To prevent batteries from exploding, keep them connected to the marine float charger that has a float setting or disconnect them and charge them fully at least once a month
  • Use corrosion inhibitor for cable connections and always inspect them for corrosion before using.

To sum up, winterization is an important step of your boats’ maintenance. While our list includes the most common recommendations, you would also want to check the owners manual for any additional steps. Keep in mind that every boat is different. The good news is the more attention you pay on how to winterize a boat in the fall, the faster you will be able to get back to sailing in spring.

Need help?

Boat builders and marinas turn to The Hope Group for components and systems.

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