How to Winterize Your Boat for Self Storage

Last Updated on March 14, 2024

By Logan Livers,

For many boat owners, it’s time to start thinking about winterizing boats and moving them to storage.

The Importance of Winterizing Your Boat

Because boats are used in the water and often have quite a bit of water inside of them, it’s extremely important to winterize them every year. Water that’s left inside your boat can expand when frozen and destroy your boat’s engine.

According to Charles Fort, Director of Consumer Protection at boat insurance company BoatUS and Associate Editor for the company’s Seaworthy Magazine, one of the biggest mistakes boat owners can make is assuming they don’t need to winterize their boats at all.

“You need to winterize your boat unless you’re in Hawaii or Key West,” says Fort. “A lot of people in Tennessee, Georgia, and Alabama don’t think they need to winterize their boats. But unless you’re in a place that never ever freezes, you need to winterize.” It only takes one freeze for your boat to be damaged.

When It’s Time to Winterize a Boat

Before you even begin to winterize your boat, it’s important to know when you need to prepare it for the winter. This will vary depending on where you live and where you store your boat. But, in most cases, it’s before the first major freeze of the season.

“You need to winterize before the potential for first freeze,” says Fort. “Boats stored out of the water will be damaged before boats left in the water because water equalizes temperature so it doesn’t freeze as soon.”

“You need to winterize before the potential for first freeze.”

Charles Fort, Director of Consumer Protection at BoatUS

Northern states will experience freezing temperatures far sooner than southern states. On average, northern states can expect this freeze anywhere from mid-September to mid-October while southern states often don’t have a freeze until after mid-November. Of course, these dates will fluctuate, so you’ll need to keep a watchful eye on the weather in your region.

How to Winterize Your Boat

While winterizing a boat can take a good deal of time, it’s not as complicated as you might think. It’s certainly a skill worth learning if you’re a boat owner, one that many people can easily do on their own.

The most important step in winterizing a boat? “You have to take out any water,” says Fort. This includes the engine and fresh water system.

Fort explains that there are two ways to get water out of boats. “One way is to drain it, but that can be problematic. Some ski boats may have two, four, or even five drain cocks, so it can be difficult to get them all. If you forget just one, your engine can still be ruined.” Due to the chances you may miss a drain cock, the second way to get the water out doesn’t involve draining at all.

The preferred method is actually to run antifreeze through your boat’s water systems. To do this, Fort says, “Take the cooling water intake, put it into a bucket of antifreeze, and let it pump through the engine. Once the antifreeze starts coming out of the engine—you’ll see it because it’s usually a bright color—you’ll know it’s all the way through.” For many boats, that will be the extent of the water that’s inside; some will have other areas that need antifreeze, though.

“Some boats will be big enough to have a marine toilet, and that’s another thing that will need to be winterized,” says Fort. “Again, you need to fill a bucket with antifreeze, place the marine pump into it, and pump that through the toilet. That will protect everything within the toilet from freezing.” If you fail to winterize your marine toilet, you risk the possibility of exploding pipes, which can be costly to repair.

Stabilizing Boat Fuel and Protecting the Boat’s Battery

You’ll also have to make sure that you stabilize your fuel tank when winterizing you boat. “For the fuel, a lot of people are worried about ethanol gas,” says Fort. “Ethanol absorbs water, and once it does, the water and ethanol can separate, and the ethanol will sink to the bottom.” In order to combat this, Fort suggests filling your gas tank completely with a high-quality fuel stabilizer.

“The reason you fill a tank completely is because fuel tanks on boats aren’t fully sealed, so air can pass back and forth. A full tank will leave less room for air, which can prevent any moisture from being drawn in.”

“Fuel tanks aren’t sealed like they are in a car, so it’s important to eliminate air from the equation.”

Charles Fort, Director of Consumer Protection at BoatUS

In fact, when storing your boat at a marina, Fort says the National Fire Protection Association requires you to fill your gas tank for safe storage. “Fuel tanks aren’t sealed like they are in a car, so it’s important to eliminate air from the equation.”

If you live in an area that experiences extremely cold winters, you’ll also want to take precautions to protect your boat’s battery. When storing your boat outdoors for the winter, you may want to remove the battery entirely. “It’s a good idea to get it on a trickle charger over the winter,” says Fort. “If you don’t do that and just keep it in storage, severe cold can freeze and crack a battery.”

Preparing Your Boat’s Engine for Storage

Aside from pumping antifreeze through your boat’s engine, you also need to prevent it from rusting over the winter. This process is known as “fogging the engine” and helps coat the inside to create a protective barrier. “To do this, you typically run the engine to get it up to temp,” says Fort. “Then, you use a fogging spray or fogging oil, and you spray the engine until it dies.”

But fogging the engine strictly pertains to boats with inboard motors. There are other types, like outboard engines, that require different methods of storage preparation.

“An outboard engine should always be left in the down position,” says Fort. “All the water inside will drain out by itself. They usually aren’t winterized, but I would caution people to check the manual.”

Another common boat engine is a stern-drive engine. “Stern drives need to be winterized because there’s a water pump inside that needs to be drained,” says Fort. “There’s intake at the stern drive that goes to the engine, so pumping antifreeze through that will take care of everything.”

How to Ready a Boat for Outdoor Storage

Aside from the internal workings of your boat, you need to protect the outside and the boat’s interior, too, especially if your boat is going to be kept in outdoor vehicle storage. Most boat owners using outdoor storage will cover their boats. “A cover will keep rain, leaves, pine needles, and critters out,” says Fort.

Even if you opt for covered storage, which provides slightly more protection than outdoor storage, you should still use a cover since awnings don’t provide complete coverage.

“If it rains and you don’t have a boat cover, having the [drain] plugs out will let the water drain out.”

Charles Fort, Director of Consumer Protection at BoatUS

You may also want to open your boat’s drain plugs when storing outside. “Most of the time, we would suggest people remove drain plugs,” Fort explains. “I say most of the time because if there’s ever a hurricane where the water rises, having the drain plugs out would cause the boat to fill with water.” While most people won’t have to worry about that, if you live near the coast, it’s something to keep in mind.

Keeping drain plugs out will also help in the case of heavy rain. “If it rains and you don’t have a boat cover, having the plugs out will let the water drain out,” says Fort.

Winterizing Mistakes to Be Aware Of

There are common mistakes people make when winterizing and storing boats that often lead to disaster. BoatUS deals with insurance claims quite a bit, so Fort has seen his fair share of people damaging boats due to improper winterization. One such mistake is using a space heater.

“There are two problems with using a heater,” says Fort. “First is right when you need the heater most, when it’s freezing cold and it’s snowing, that’s when power often goes out. Second is every year we have claims about fires caused by heaters left on a boat.” Also, there aren’t any space heaters designed for use on a boat, so they can easily be knocked over and start fires.

“I think most storage operators wouldn’t allow a heater in storage on a boat, which is definitely a good idea,” Fort adds. “Boats are often made of fiberglass, and that’s very flammable. The worst part is that it doesn’t just burn your boat, but it can burn down things around it.”

For full list of proper winterizing tips, visit BoatUS’s Boater’s Guide to Winterizing.

Storing Your Boat for the Winter

Once you’ve winterized your boat, it’s ready for storage. There are many factors to consider when choosing the best storage facility for your boat, especially when you want to protect it during the winter. Since your boat will have been winterized prior to storage, it’s perfectly fine to keep it outdoors. However, covered and indoor storage offer more protection that could be worth the additional cost for some boat owners.

Colleen Shanley, on-site manager for Extra Self Storage in Red Bluff, Calif., says their storage facility offers outdoor, covered, and commercial-sized storage units for indoor boat storage. As far as recommending a certain type of boat storage, Shanley says it depends largely on your budget.

“The climate will vary at different locations, but if a person can afford the small difference in price, storing one’s boat inside is always recommended,” Shanley says, adding that many boat owners choose outdoor storage since it’s more affordable.

“…if a person can afford the small difference in price, storing one’s boat inside is always recommended.”

Colleen Shanley, on-site manager with Extra Self Storage

The downside to storing a boat outdoors, Shanley explains, is that renters must provide their own protection (that is, a boat cover) against water damage to the boat’s interior and motor. “If storing outside, it’s important to cover the wheels to protect from sun damage,” she adds. “It’s also important to make sure the cover is secure so that it’s not blown off in high winds.”

When looking for boat storage, do your homework. Not all self storage companies are created equal, so Shanley suggests you contact the management first. “It would be wise to call and see if boat storage is an option and what, if any, are the specific requirements.” You should also ask about the security features each facility offers, which could range anywhere from gated access to video surveillance.

Whether you do the work yourself or hire someone else to do it, winterizing your boat is crucial in order to extend the lifespan of your boat and prevent damage during its time in storage.

Read more:
How to Winterize Your Car for Self Storage
How to Winterize Your Motorcycle for Self Storage
How to Winterize Your RV for Self Storage



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