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Winter Is Coming: How to Winterize Your Boat Like a Professional

by Jonathan Eldridge
Winter Is Coming: How to Winterize Your Boat Like a Professional

Whether we like it or not, all seasons must end.

The boating season must eventually come to a close.

If you live in a year-round boating destination, consider yourself lucky.

Also, why are you even here?

Are you just gloating over being able to boat around Florida while we freeze our butts off in January?

Then you can show yourself to the exit go enjoy some of our blog posts about boat party accessories and fun boating gadgets you can install this weekend.

Since I assume most of you are here because you're staring down the barrel of winter weather, then we've got your back. Consider some of these tips and instructions to properly winterize your boat.


Hiring a professional to take care of boat winterizing tasks is always a splendid idea, however, that can also be expensive.

If you just take it slow, and maybe enlist the assistance of a boating buddy or a willing teenager (bribery is always an option), you shouldn't have a problem.

The information below comes from experience, but you know your own boat better than anyone.You should use your best judgement about what your boat needs, and also refer to your boat owner's manual for specific information on your particular make and model. For example, you'll want to make sure that certain types of antifreeze, such as alcohol-based antifreeze, are okay to use on your boat.

Products Needed to Winterize Boats

Once you've marked off a time to work on winterizing your boat, you'll want to make sure you have the necessary items to get everything done.

Along with the various hoses and model-specific parts, products like fuel stabilizer and fogging oil are necessities.

Here are some of the main products you'll need to complete this winterization project.

  • Fuel Stabilizer Surprisingly, gasoline does decompose over time. It can form deposits that harden in your boat's fuel tank. A fuel stabilizer, such as STA-BIL (check price on Amazon), keeps the fuel fresh and prevents buildup while it's stored over the winter. It eliminates the need to drain the fuel tank, and your boat will start up nice and easy in the spring.
  • Marine Antifreeze Just like in a car, antifreeze (check price on Amazon)is essential to protecting your boat's hoses, engines, water systems and other components over the winter. Unlike a car, though, you'll want to make sure you use a marine antifreeze.

Boats have a circulation system that pulls water in from the lake, river or ocean, then sends it through the engine block before discharging it back into the water. Automotive antifreeze is very toxic, making it a bad choice for both marine systems and the environment. RV antifreeze tends to have similar properties to marine antifreeze, and can be a good choice too.

Choose an antifreeze made with propylene glycol as it's odorless, tasteless and non-toxic as well as biodegradable.

  • Fogging Oil There are many valves and steel and iron parts in a boat motor.Fogging oil (check price on Amazon)lubricates these internal parts and repels moisture to prevent rust.

How to Winterize Boat Motors

The motor is probably the single most important, and most expensive, feature on board your boat.

You'll want to ensure that it's properly winterized to eliminate the need to repair it or buy a new one come spring, both of which can be extremely expensive.

While the general concept is similar, there are a few differences in winterizing inboard, outboard and I/O (sterndrive) motors. And, yes, even jet-ski motors need to be winterized.

How to Winterize Outboard Motors

Before you start on the actual process of winterizing, you'll want to clean barnacles and other debris from the propeller and motor. This is a good job for that bribe-taking teenager.
  • Put a fuel stabilizer in the gas tank.
  • Run the tank with fresh water.
  • Flush with marine antifreeze and fog with fogging oil.
  • Store the engine in a vertical position so that if any water remains, or somehow gets inside over the winter, it drains out.
  • Lubricate grease fittings.
  • Remove the propeller and grease the prop shaft. Replace it when done.

How to Winterize Inboard and I/O (Sterndrive) Motors

Inboard and inboard/outboard (a.k.a. sterndrive) motors require the same type of techniques when winterizing. Proper winterization is crucial on this type of engine, as any amount of water can crack the block.
  • Put STA-BIL in the fuel tank.
  • Start the engine and get it up to temperature.
  • Flush with marine antifreeze and fog with fogging oil.
  • Change the oil and the filter.
  • Remove water drain plugs in the exhaust manifold and the engine block if available for extra protection.
  • If there are no plugs on the block or exhaust, remove the thermostat to flush with antifreeze. Replace the thermostat when done.

How to Winterize Jet Drive Motors

You thought you were going to get out of this one didn't you? Even though they don't have a propeller or a traditional motor, jet-skis and jet boats still require winterization. The nice thing about a jet-ski is that it can be easily stored inside a garage over the winter.
  • Put STA-BIL in the gas tank and fill the tank.
  • Flush with marine antifreeze. You'll need a pump, as jet-driven engines don't have a water pump of their own.
  • Change the oil if it's a four-stroke.
  • Fog the engine.
  • Take out the battery and store it inside over the winter.

How to Winterize the Fuel Tank of a Boat

Since gasoline contains a small amount of water, it's very important to winterize the fuel tank. Even a small amount of water can freeze and cause a lot of damage to your boat's fuel tank.

Even if it doesn't freeze, the water will sink to the bottom of the tank and sit there waiting to run through the engine (rather than the gas that's supposed to run through it). This can also cause problems.

There's apparently a debate on whether it's best to fill the tank to the top or leave it completely empty. Both sides have their opinions. From personal experience, if you use a good fuel stabilizer, you should be just fine to leave some gas in the tank.

  • Change fuel filters.
  • Fill with fuel and add a fuel stabilizer like STA-BIL.
  • Change the water separators.

How to Winterize the Bilge of a Boat

Boats that stay in the water over the winter don't need the bilge pump winterized. You'll just want to make sure it's working correctly. If your boat is going ashore for winter, here are a few winterizing tips:
  • Clean with soap and water.
  • Spray with a moisture-displacing lubricant.
  • Use antifreeze to prevent water from freezing.

How to Winterize the Hull of a Boat

If your boat is going to be stored out of the water for the winter, this is a great time to give the hull a little TLC. Some boat owners use this time to have the hull repainted if it's necessary. A few other things you'll want to do include:
  • Check for cracks, dents and chipped paint.
  • Remove barnacles and debris from the prop, rudders and other exposed parts.
  • This is also a great time to give the hull a thorough cleaning and waxing.
  • Take into consideration whether your boat will be stored in or out of the water. If stored in water, close the seacocks. If stored on land, open the seacocks so water can drain out.

Winterizing the Interior of a Boat

Boats with cabins require a bit more time when it comes to winterizing. Along with the obvious tasks of draining water systems, adding antifreeze and pumping out heads, interior vinyl and storage areas should be cleaned and prepared for winter weather.
  • Condition vinyl against drying and mildew by polishing with a marine vinyl protectant.
  • Clean drawers, cabinets and other storage areas and leave them open. You don't necessarily have to remove the items, but this will prevent them from smelling moldy and musty the next time you open them, which could be several months away.
  • Clean and disinfect the refrigerator and freezer. In this case, you probably should remove all items. If you have to ask why, you've never returned to a six-month-old science experiment in your boat's fridge.
  • Pump out the head, flush with fresh water, add antifreeze and pump through all of the hoses and valves.
  • Drain the fresh water systems and hot water heater. Disconnect the lines on the hot water heater and then connect them. Flush the system with antifreeze. Fill the water heater with antifreeze.

Winterizing the Cover and Accessories of a Boat

Boat covers need a little love and attention too. One bad storm could pull the cover right off of your boat, or, at the very least, fill it with rips and tears. To avoid this, make sure that it's sturdy enough to withstand harsh conditions. Choose a heavy canvas cover that's water-resistant and large enough to cover the waterline of the boat. Another option is shrink wrapping. This is usually done at a marina or boat storage yard, and it can get quite expensive. Here are a few tips for the traditional canvas cover:
  • Use insect and rodent repellent to steer clear of spiders, bees, mice and other troublesome creatures. You don't want to pull that cover off next spring and be rewarded with a swarm of bees. Just trust me on that one.
  • Put some padding on sharp corners, such as around windshields, to prevent wearing through the cover.
  • Make sure that there are no dips in the cover where rain or snow could collect.
  • While you're on deck, give the vinyl chairs and seats a good going over with some vinyl cleaner. It's a good idea to store removable cushions indoors over the winter.

On a side note, if your boat does need preventative maintenance, a tune-up, new hoses or water pump work, now might be just the time to do it. Many marine shops offer a lot of preventative maintenance in their winterization packages. Why not schedule it now while you're not using the boat anyway? This will get you out on the water a lot quicker than if you try to get all of that done in the spring when shops are busy with other boats that waited until spring. I

t may seem like a lot of work, not to mention all of the sadness, to put your boat to bed for the winter. But the time and care you take now will ensure that it stays cold-weather safe and is ready to go in the spring.

Your boat will thank you.

Hopefully these tips have helped you decide that winterizing your boat isn't such an intimidating task. Before you know it, you'll be a pro and your friends will be asking you for help with their boats. On second thought, maybe you'll want to keep that newfound knowledge to yourself. Happy winterizing!

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