How to Winterize a Boat - Full Guide to Prepare for the Winter Season

Not all boat owners live in tropical climates where weather stays warm year-round. While living on the constant 100+ degree equator poses its own challenges for seacraft, those living where the seasons change have another concern - winter.

As the final jacket-free days of fall begin to wane, it's time to turn your attention to your boat and prepare it for incoming freezing temperatures.

Why Should You Winterize Your Boat?

Most boats live perpetually outdoors, often in the water. Without the right precautions, boats can't handle the constant freezing and thawing of water.

Ice will build up on the surface of the boat, but more than that, any moisture in the electronics will crystalize, too. Rubber components can become brittle and crack, ice can expand inside joints and burst seals, and hulls can crack.

In short, winter weather can cause expensive damage to an unprepared boat. Whether you store your boat in a heated, climate-controlled storage unit, on a trailer in your yard, or tied up at the marina, winterizing will ensure the boat is ready to use come spring.

Collect Your Materials

To protect your boat for winter, you'll need:

1. Microfiber cloths (when you spill liquids, these cloths won't scratch surfaces)
2. Fresh engine oil
3. Fuel stabilizer
4. Antifreeze
5. Oil filter
6. Motor flush muffs
7. Fogging oil
8. A boat cover or boat wrap
9. A dehumidifier or desiccants

If flexible or rubber parts of your boat have been damaged, such as hoses or gaskets, it's best to replace them while the weather is still warm and your boat is not yet in storage.

Winterizing Your Boat

Winterizing your boat isn't just about preventing freeze damage - it's about setting yourself up for a smooth start to next season. The best time to do it is before overnight temperatures drop below freezing. Waiting too long makes the job harder and increases the risk of cracked hoses, frozen water lines, and engine damage.

1. Change the Engine Oil and Filter

Start by warming up your engine. If your boat is still in the water or connected to a freshwater source, use motor flush muffs to circulate water through the cooling system while the engine idles. This helps the oil thin out so it drains completely when you change it. Refill with clean oil, replace the filter, and run the engine briefly again using the flush muffs to circulate the new oil.

2. Fog the Engine

Fogging helps protect internal engine parts from corrosion while your boat is in storage. For carbureted engines, use a standard fogging fluid; for EFI (electronic fuel injection) engines, use EFI fogging oil or a fuel mixture designed for that system. Once fogged, check your gear oil for signs of water contamination - if it looks milky, drain and replace it.

Learn more about winterizing your boat engine in our related blog.

3. Stabilize the Fuel

Fuel can degrade over time and lead to gummed-up lines and injectors. Add a marine fuel stabilizer to your tank, then run the engine for several minutes (again using motor flush muffs if out of the water) to ensure treated fuel reaches the entire system.

4. Flush, Drain, And Add Antifreeze

Drain all freshwater and raw-water systems, including washdowns, live wells, and any onboard plumbing like sinks or heads. Then, use marine-grade non-toxic antifreeze to fill these systems. Flush the engine's cooling system one last time and circulate antifreeze using your motor flush muffs until you see the pink fluid exiting the exhaust.

5. Lubricate And Protect

Grease all fittings and moving parts and apply a marine-grade corrosion inhibitor to exposed metal. A few extra minutes here can prevent seized components and surface rust down the road.

6. Clean And Wax Your Boat

Give your boat a full cleaning inside and out. Remove salt, grime, and stains with marine-safe cleaners, then apply a protective wax coat to the hull and topside surfaces. A clean, waxed surface will resist oxidation and be easier to prep in the spring.

7. Cover and Dehumidify

Finish by covering your boat with a breathable, well-fitted cover. If it will be stored outside, ensure the cover is tight and water-shedding. Use moisture absorbers or a small dehumidifier to reduce the risk of mold and mildew forming during storage.

Get Your Boat Ready for Next Season

Winterizing your boat takes a little time now, but it pays off with fewer headaches and repairs when spring arrives. Protecting your engine, fuel system, and interior surfaces keeps your boat in top shape and ready to hit the water as soon as temperatures rise.

With the right tools and products-like motor flush muffs, marine-safe antifreeze, and Captain's Preferred Products cleaning supplies-you can make the process faster, easier, and more effective. A little preparation today means more smooth sailing tomorrow.