Winterization Guide: How to Protect and Store Your Boat

Last Updated on October 18, 2024

As a boat owner, you know how important keeping your boat safe during the cold months is – using indoor or outdoor boat storage. Winterizing your boat helps prevent damage from the harsh winter weather and ensures it’s ready to go when the next season starts.

Whether you have a stern drive, inboard or outboard engine, and no matter the size of your fuel tank, this guide will walk you through each step, from flushing the engine to covering and storing your boat the right way as well as options for winter boat storage.

Step 1. Flush and Drain the Engine

No matter your boat engine, the first step is to flush it with fresh water. Before you do that, though, make sure you have the owner’s manual handy, as each engine model may require different procedures.

If you don’t know where you’ve put it, chances are you can find it online. Top boat manufacturers have PDF manuals on their websites for all current models.

Checklist for outboard engines

  • Attach water muffs to the engine and run fresh water through until it reaches its optimum operating temperature.
  • Ensure all water drains out completely to prevent freezing damage.
  • Wash the motor’s exterior with soap and water, then rinse thoroughly.
  • Drain the carburetor, lubricate moving parts and apply fogging oil to the cylinders.

Checklist for inboard engines

  • Run fresh water through the engine using a garden hose.
  • Circulate antifreeze through the cooling system after flushing to prevent freezing.
  • Spray each cylinder with fogging oil to protect against corrosion.
  • Wipe down the engine with a WD-40 sprayed cloth to displace moisture.

Pro Tip: Inspect hoses periodically for wear and replace them as needed to help avoid costly leaks or other damage.

Step 2. Treat the Fuel System

You want to treat your boat’s fuel system right before winter, so it won’t cause problems as you power up the next boating season. Here’s how you do that:

  • Add a fuel stabilizer to prevent fuel degradation and varnish buildup for up to 24 months.
  • Start the engine and let it run for at least 10 minutes. This way, the stabilized fuel has enough time to move throughout the whole system.
  • Fill the fuel tank to approximately 90% capacity. This prevents condensation buildup while allowing room for fuel expansion.
  • Replace the fuel filter and/or water separator to ensure clean fuel flows through the system.

Recommended fuel stabilizers: PRI-G and STA-BIL.

Step 3. Drain and Protect the Plumbing

Now, on to the plumbing! First, winterizing antifreeze is not the same as engine antifreeze and cannot be used the same way. You must use only propylene glycol antifreeze in freshwater systems. It’s environmentally friendly and safe for human contact, whereas ethylene glycol is potentially lethal. Also, you should use it at full strength and not dilute 50/50 with water as with engine antifreeze.

Now, here’s how to do it step by step:

  • First, drain the freshwater systems entirely, including sinks, tanks and hot water heaters. Just open all faucets and allow water to drain until the system is empty.
  • Add non-toxic, propylene glycol antifreeze to the freshwater tank and run it through the entire system by turning on each faucet, starting with the one farthest from the tank.
  • Pump antifreeze through the head(s) and other systems like livewells and washdowns to prevent freezing.
  • Check the drains, as some lines could be holding water. Blow it out with compressed air, then pour antifreeze directly into the drain.

Pro Tip: Read antifreeze labels carefully, as some formulations are only good down to certain temperatures.

Step 4. Clean and Wax the Exterior

Before tucking your boat for winter sleep, thoroughly clean its exterior, apply a protective wax coating and inspect and clean the propeller, along with other exterior components.

  • Use a pressure washer to remove any barnacles, algae or marine life from the hull.
  • Clean the entire boat, including the topsides, deck and bottom, using a proper boat cleaner.
  • Pay special attention to crevices and clean all surfaces such as fiberglass, teak, vinyl and canvas.
  • Once your vessel is clean and dry, special boat wax should be applied to the hull and all other exposed fiberglass surfaces. This procedure adds a layer of protection, helping the boat withstand temperature changes and preventing algae growth.
  • Check for nicks or dents in the propeller and clean it. While at it, check for signs of corrosion on any outside components and apply an anti-corrosion treatment where needed.

Step 5. Remove and Store Valuables

Valuables and electronics are better off stored separately from your boat during long-term storage. To make sure you don’t miss anything, here’s a quick checklist:

  • Clear the boat of personal effects, fishing gear and portable electronic equipment such as GPS units and radios. Don’t leave first aid kits or life jackets behind, either.
  • Keep them in a dry place and safe location to protect them from thieves and damage during the off-season while you’re using indoor boat storage.
  • Make a very detailed checklist of all items you remove from the boat. Checklists allow you to keep track of everything, so in this way, nothing gets forgotten or lost.
  • Use the checklist again when ready to re-equip your boat in the spring.

Pro Tip: Storing your devices in a climate-controlled indoor boat storage unit will protect them from moisture and temperature changes.

Step 6. Lubricate Moving Parts

From the engine to the gear, let’s make sure everything is properly oiled for winter boat storage.

  • Apply a high-quality lubricant to all moving parts, including steering systems, throttle cables and propeller shafts. This prevents rust and wear during storage.
  • Keep the fittings and joints well lubricated to stay smooth and operational.
  • Warm up the engine to normal operating temperature, then change the engine oil to eliminate moisture and acids that accelerate corrosion.
  • Replace the oil filter to ensure the engine a fresh start next spring.
  • Also, change the gear oil in the lower unit to protect the transmission from moisture and corrosion.
  • Besides the engine oil and gear oil change, it’s also important to check and replace other fluids, like coolant, steering fluid, and outdrive oil, depending on your boat’s specific requirements (when in doubt, check the manual from the manufacturer).

Pro Tip: Always inspect the old oil when replacing it to catch signs of contamination early on. For instance, if you notice a milky color, there’s water in the oil. This calls for professional attention.

Step 7. Empty and Clean the Bilge

Keep your boat’s bilge clean and dry during winter storage to prevent odors, mold and, why not, potential damage.

  • First, drain all water from the bilge. Do this by removing the drain plugs (if your boat is on dry land) and ensuring the boat is properly positioned for thorough drainage.
  • Scrub the bilge area with soap and water to remove any accumulated dirt, oil and grime. If you’re green-minded, use a biodegradable bilge cleaner and let it soak before scrubbing.
  • Rinse the bilge with fresh water and dry it completely to prevent mold and rust. Capture any wastewater for proper disposal at a waste management facility.
  • If you can’t remove all the water, add a small amount of antifreeze to prevent any leftover water from freezing during the winter.

Step 8. Check and Secure Drain Plugs

Remove all the drain plugs and store the boat with the bow raised to prevent water from accumulating in your boat during storage on land.

Note that water can still get inside even with covers, so removing the drain plugs and keeping the boat in this position will help the water drain and prevent pooling.

Step 9. Cover the Boat

Now that you know how to winterize a boat, it’s time to choose a high-quality cover to help protect your boat from rain, snow and debris. Here are some useful pointers:

  • Plastic covers are the cheapest option but only last a few seasons.
  • Canvas covers are durable and allow for air circulation.
  • Shrink wrap offers a snug fit and maximum protection.

Did you choose a canvas cover? Make sure the cover has adequate ventilation to prevent mold and mildew but cinch it tight, so it does not come loose in strong winds. This also helps keep water out of compartments and crevices, thus preventing freeze damage.

If you go for shrink wrap, don’t attempt a DIY project; get an expert to do it — they know where to install vents to allow air circulation. Then, come spring, check with your marina or boatyard for shrink-wrap recycling programs.

Additional Tips and Considerations on How to Winterize a Boat

Going through the full winterization process for the first time is not an easy task for boat owners, so be sure to avoid these common mistakes that can damage your watercraft and incur hefty costs:

  • Incomplete winterization, typically by skipping steps like draining water systems or not properly sealing the boat.
  • Poor ventilation under covers, which can lead to mold and mildew growth.
  • Neglecting security, as boats stored long-term can be targets for theft. Stow all valuables. Lock up hatches. Add extra security measures like wheel locks or GPS tracking systems.

Your boat is all prepared for the winter, but where will you store it until the next boating season?

  • Indoor boat storage offers the greatest protection against the elements, reducing the possibility of damage directly linked to weather conditions. It’s the go-to choice in areas with harsh winters.
  • Outdoor boat storage is cheaper but requires an expensive cover or professionally applied shrink wrap to protect the boat from rain, snow and UV damage. An outdoor storage option is only ideal if you live in a moderate climate.

Pro Tip: DIY winterization can save money, but if you’re unsure about any step, consult a professional.

Boat Owners, Winterize!

When you take the time to winterize your boat, you make a commitment to protect your investment from the damage that winter weather can bring. By thoroughly flushing the engine, treating the fuel system and ensuring every part of your boat is clean, dry and well-protected, you’re setting the stage for a hassle-free start when the boating season returns.

Storage.com offers a range of options and prices to find an indoor boat storage facility and discover the range of winter boat storage options.

Andreea Draguleasa showed an affinity for foreign languages and literature at an early age and started writing when she was 6. She studied journalism, advertising, and public relations at the University of Bucharest and worked as a content writer for a tourism agency and as a journalist for a magazine in the hospitality industry until 2010. After seven years as marketing manager for a Home & Deco online shop, she realized that learning something new every day brings her the most joy, so she went back to researching and writing informative articles. Through her experience traveling the world, she's picked up tips and resources she now shares on self storage solutions. When not writing about home organizing and storage, Andreea spends most of her time reading, playing video games, and spoiling her cat.