How to Winterize Your Boat

How to Winterize Your Boat

October 26, 2017

01 Winter Boat Maintenance Checklist

The fall chill is in the air, reminding many of us across the country that our boating days are coming to an end. While it’s easy to shift your focus to fall activities and pack up your boat for the winter in a hurry, we’re here to remind you that to maximize the life of your boat — and to minimize the costs due to winter damage — you need to prep your boat for winter.

Preparing your boat for winter is also known as winterizing. Winterizing your boat is time-consuming, and you may choose to hire professionals to do it for you. If you do decide to hire a professional, it’s important to hash out the details beforehand. “Winterizing” doesn’t mean the same thing to everybody, so the best way to ensure you’re getting the service you expect is to have a written contract of what the company will be doing to prep the boat for winter.

But for those of you who are interested in doing all, or some, of it yourself, we’ve compiled a list of tips for preparing your boat for winter, so you know how to winterize your boat.

The specific steps you’ll need to talk to prep your boat for winter will depend on the type of boat you have, so it’s important to consult your owner’s manual, which should have a winterizing or storage section. The section will give you the best care for your boat in the off-season.

Overall, there are certain tips for preparing your boat for winter that apply to all makes and models, but there are also specifics that vary depending on the type of boat and boat features. We’ve done our best to make this a comprehensive list, calling out details when appropriate, so you know what winterizing looks like for your specific make and model.

1) Take Care of Any Required Maintenance in the Fall

When the weather starts to get warmer and spring fever is upon us, boat shops are in the midst of their busiest season — which means you’ll have longer wait times and a delay getting your boat back in the water. Rather than rushing the process of winterizing your boat, use it as an opportunity to thoroughly check and make sure everything is working well and that the exterior and interior of the boat are in optimal condition.

If something is out of place or doesn’t seem to be running smoothly, fall is the best time to get it in for maintenance. Fall is also a great time to get your routine maintenance done. After that, a thorough winterization means your boat is in its best shape and ready for the first sign of spring.

2) Determine Out-of-Water or In-Water Storage

Ideally, you’d store your boat in a climate-controlled warehouse during the off-season, but for most, the price tag that accompanies that type of storage is next to impossible to afford. If you live in an area that doesn’t usually see temperatures near or below freezing in the winter, you may store your boat in the water, or out of the water. Here are a few pros and cons of each storage option.


  • No hauling to/from in-season location
  • Ready for use at the first sign of spring
  • Fewer steps involved for winterizing
  • Increased water scum and marine organism growth
  • Risk of sunken boat


  • Requires additional hauling to/from marina
  • Needs some prep before being ready in spring
  • Reduces risk of blisters on fiberglass hull
  • Less vulnerable to damage from sudden freeze or storm

Once you’ve decided, there are a few winterizing tips specific to each of these storage options. If you decide to store your boat out of the water, you want to make an effort to clean all exterior surfaces thoroughly and to open seacocks to drain water.

On the other hand, if you decide to store your boat in the water, your focus should be on ensuring all seacocks are closed, and that pumps and your battery are working together to turn on the boat when necessary to drain water. Checking for leaks is important for all boats, but especially for a boat that will be stored in the water, as a leak could lead to a sunken boat.

3) Invest in a Boat Cover and Frame

One of the reasons winter can be so harsh on your boat is exposure to the elements — cold, snow, ice, rain, etc. Regardless of where you store your boat for the winter, you’re going to need to invest in a boat cover and frame.

The key to finding the best boat cover is fit. If you try to make one of the one-size-fits-all covers work, chances are you’ll end up with something that is either too big — which welcomes pooled water and wind — or too small — leaving areas of your boat exposed or stretching the cover in a way that can cause its own set of problems. If your owner’s manual or manufacturer doesn’t have a specifically recommended cover for your boat, there are plenty of places you can go to get a custom cover, which is sure to give you the best fit.

Frames are temporary structures you can assemble and put on top of your boat, underneath the cover. They are essential because they keep the amount of snow, pooling water and debris on top of your boat to a minimum. Any snow, water or debris that does manage to accumulate on your boat cover is evenly distributed by the support, decreasing the chance of damage to your boat due to unwelcome weight.

4) Change the Oil and Oil Filter

Inevitably, oil in your boat can get water and other contaminants in it over time. The composition of oil can change over time, becoming more acidic. When it sits for an extended period — like over the winter — the water and contaminants sit in the engine, which can cause expensive damage.

Changing the oil and oil filter right before you store your boat for the winter can save you from an expensive surprise when you uncover the boat next season. Don’t forget to let the engine run for a few minutes before you change the oil — that ensures any contaminants have a chance to become suspended in the oil before you change it, so you can minimize the contaminants that are left when you change the oil. The oil change is also a great time to check for any oil leaks.

5) Pressure Wash and Inspect Your Boat Bottom

03 Pressure Wash Boat

Over time, barnacles, dirt and other water scum are bound to accumulate on the bottom of your boat. Before you store it for the season, dedicate time to scraping and sanding it all off. Follow the scraping and sanding with a thorough pressure wash. In the future, you can decrease the amount of scraping, sanding and scrubbing by applying a wax at the beginning of the season.

Once you’ve thoroughly cleaned the bottom of your boat, inspect it for cracks, blisters and dents. If you discover something minor, you may be able to fix it yourself with a filler or rubber mallet. If you discover something serious, have a professional look at it. Any cracks or blisters can become a nightmare with cold temperatures over the winter.

6) Change the Fuel Filter and Stabilize the Fuel

Don’t neglect to change your fuel filter and/or canisters and check for leaks before you store your boat for the off-season. Stabilizing fuel as a step to prep your boat for winter ideally begins before your last day on the water.

Assuming your boat runs on gasoline and has ethanol in it, it’s at risk for something called phase separation, which occurs when the ethanol in the gasoline absorbs moisture to the point that it separates from the gasoline and causes damage to your engine.

Your best-case scenario is to empty the fuel tank, so absolutely nothing is in it. Since that’s often not practical, the next best thing is to stabilize the fuel.

There are a variety of stabilizers available — your manufacturer may recommend one. Regardless of which you choose, add it when you still have a few boating days left, so it has time to completely and thoroughly circulate throughout the fuel system. Then, top off your tank to 95 percent full. With the fuel tank this full, there is less room for moisture to accumulate. Treat it with fuel stabilizer again, and let the engine run for a bit to circulate. Now your fuel is prepped and ready for winter.

7) Use a Mildew Spray on Interior Surfaces

It’s always important to care for the interior of your boat, but this becomes especially important during the winter. While a strong boat cover and frame are perfect for protecting it from the elements, they can also be a trap for moisture.

Making sure your boat cover has a vent — many are available that connect right to the frame and cover — is a great step to reducing moisture. But, to provide the ultimate protection for your interior, consider coating the interior of your boat with a mildew spray before applying the boat cover and storing it for the winter. This step can help save you from a major cleaning project in the spring.

8) Remove Electronics From the Interior

In addition to causing mildew, moisture can corrode your electronics, causing shorts and blown fuses — two things that can be expensive to repair. Before you cover your boat for winter storage, remove any electronics you can and store them in an environment that’s protected from winter temperatures and moisture. For the electronics you can’t remove, spray exposed electrical connections with a moisture-displacing lubricant to help protect them from moisture.

9) Drain the Water From the Engine and Add Antifreeze

Regardless of what type of engine you have, draining and flushing the system with antifreeze is essential. However, the steps taken vary depending on the type of engine on your boat. We’ve listed an overview of the most common below, but it’s important to remember your owner’s manual will have the best, most specific information on winterizing your boat.


To winterize an outboard engine, use flush muffs or the flushing port on the back of the engine. Start the engine, remove the cowl and spray fogging oil into the air intakes on the front of the engine to circulate throughout the system to prevent rust and corrosion. Keep the engine running while you disconnect the fuel line from the engine, and continue to spray the fogging oil until the engine dies. This step ensures all fuel is burned and prevents buildup that can occur due to evaporating fuel. Next, move on to the propeller — apply water-resistant grease to the propeller shaft and threads. Finally, lubricate or polish the engine exterior and wash it with soap and water, making sure you rinse it thoroughly.


To winterize an inboard engine, use the water pump and intake hose. Dump antifreeze into a bucket, then stick one end of the intake hose into the bucket. Start the engine and let it run until the antifreeze exits the exhaust, assuring you it has circulated throughout the system. It’s also a good idea to change your transmission fluid, remove spark plugs and spray fogging oil into each cylinder to prevent rust and corrosion during the off-season.


    Winterizing a stern drive begins with a thorough visual inspection of the lower section, removing any plant life or barnacles you find. Then, clean it with soap and water. Check for cracks or pinholes in the rubber boot between the transom and engine, if you have one. Finally, make sure to grease fittings and check your fluid levels in hydraulic steering or lift pumps.

    10) Drain the Freshwater System and Add Antifreeze

Freezing water can be a nightmare for boat owners. While draining your freshwater system is a start, the reality is that water can linger in areas throughout the system — and it doesn’t take much water to be able to freeze and cause a disaster in the form of cracked pipes, valves and pumps. So, in addition to draining every part of your freshwater system, you also want to be sure you circulate antifreeze throughout to ensure freezing will not occur.

Start with shutting off your dockside hookup and draining the hose. Open all outlets to drain water, then close them, pour antifreeze and reopen outlets to ensure antifreeze is throughout your freshwater system.

11) Disinfect Marine Head and Add Antifreeze.

Marine heads come in all shapes and sizes — with and without holding tanks and as part of a sanitation system. While the method may be different for each, the bottom line is the same — you’ll need to disinfect and add antifreeze.

If your toilet doesn’t have a holding tank, simply pour disinfectant into the bowl and pump it throughout the system, followed by antifreeze. If you have a holding tank, make sure you empty it before you pump disinfectant and antifreeze through the tank and the “Y” valve, if you have one.

Marine sanitation systems can be tricky, and winterizing techniques vary, so for the best advice, consult your owner’s manual.

12) Remove Oil and Water From Bilges05 Boat Clean Oil Spills

Over the course of a boating season, bilges can collect oil and water. It’s important to clean any oil spills thoroughly. Even if the amount of oil is small, give the bilge a meticulous cleaning. Then, add a moisture-displacing lubricant to deter the accumulation of moisture during the winter. Finally, add a little bit of antifreeze to ensure any water that may collect over the winter months will not freeze and cause damage to your boat.

As you can see, there are several steps involved in prepping your boat for winter. Failing to remember a step or failing to complete a step correctly could result in expensive repairs. While this guide provides insight on how to winterize your boat, the ultimate guide is your owner’s manual. It’s always best to consult that resource to get specific tips for preparing your boat for winter.


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