Boating Basics: How to Winterize Your Boat

Post by - Published on 09/02/22 16:00 PM

Think again if you plan to wait for spring to get professional help, as it’s the busiest time for boat mechanics. Therefore, as the saying goes, don’t put off tomorrow what you should do today. Even if you’re a snowbird who’ll use your boat all winter long, now is the time to check on those systems and items aboard that’ll need some maintenance before hitting the icy waters to protect it from the elements.


What is boat winterization?

Boat winterization is changing the oil, fogging the engine, greasing the gears, etc. There are several–13 to be exact– steps you'll need to take to ensure your boat, its motor, and systems are ready to go when the snow melts and the weather warms. 

Why is winterization important for all boat owners?

Failing to protect your vessel’s engine, air conditioners, potable water, or other systems against freeze damage can result in costly repairs or, worse, the loss of your boat. But, of course, if you keep your boat in a place like Boston, Minneapolis, Vancouver, or Chicago, where winter weather is extreme and unpredictable, or the ice can get up to three feet thick, you probably don’t need much convincing. 

Boaters in sunny, temperate climates like San Diego, New Orleans, or Corpus Christi aren’t off the hook! According to the marine insurers at BoatUS, these states generate the highest number of freeze-related insurance claims.

How much does it cost to winterize a boat?

If you go the DIY route, it will cost you about $250. If you take it to a professional mechanic, you're looking at $500 up. Like most things, it all depends on the size of your boat. For smaller boats,  winterizing might mean disconnecting the battery and the portable fuel tank then draining the fuel from the engine. Winterizing is costly for larger boats with inboard power plants, water systems, live wells, heads, and gallies. 

How to Winterize a Boat: A Step-By-Step Checklist

Winterizing your boat is necessary if you want to enjoy a hassle-free splash in the spring. Below you’ll find 13 easy steps on how to do it:

Step #1. Drain the engine

For inboards and stern drives, you'll need to locate and open the petcocks underneath the manifolds and on the sides of the engine block. Some engines will have bronze plugs similar to bilge plugs. Next, remove the water-pump hose from the bottom to let it drain completely. 

Draining the engine will ensure the water in the cooling chambers can't freeze, expand and crack the engine block and manifolds, costing you up to tens of thousands of your hard-earned cash.

Step #2. Check the hull 

While fiberglass is made to stand up to the sun, sand, and saltwater, some snow will be its kryptonite. Snow eventually becomes ice, and when water freezes, it spreads, which can cause open hatches and window tracks to split, causing leaks. If you plan on utilizing outdoor storage, your boat will need a cover.

You should also check for stress cracks around the bow eye and Gelcoat blisters as they indicate structural damage. Accordingly, a professional should look at it if this is the case. Next, If your hull is aluminum, bang the drum slowly with a rubber mallet to knock out dents. After you work out your frustrations on the hull, scrape off any barnacles, and other unwelcome hitchhikers stuck to your boat's bottom and sand away any residue. Finally, a power wash will remove all other sea scum and dirt.


Step #3. Replace engine oil

Changing the engine oil is a must to eliminate moisture and prevent corrosion, as old oil in the crankcase of a stored boat forms acids. Extra water and humidity cause excessive wear, leading to loss of power, poor fuel economy, and possible engine failure. 

Step#4. Fog the engine

Just as changing the oil prevents corrosion, fogging prevents corrosion of inboard or outboard engines stored for an extended period. Fogging oils and sprays are specially formulated to penetrate deep into the engine and coat parts with a protective layer of anti-corrosive compound until spring. 

Hook “ear muffs” and a garden hose to the engine, start it, and then spray the fogging-solution lubricant directly into the air intake until it’s gone.

Step #5. Add a high-quality fuel stabilizer

The next step is to treat your boat’s fuel with a stabilizer to ensure carburetors and fuel injectors won’t get clogged with varnish deposits that ruin fuel systems. After adding the stabilizer to the fuel, run the engine for at least ten minutes, so it circulates throughout the engine.


Step #6. Drain gear-case lubricant

Check the color of the liquid while draining the gear case, as it will indicate potential issues. If it's clear or amber-colored, the gear-case is well lubricated. If it's milk-colored, there may be water in the oil, meaning you'll want to replace the seals over the wintertime. If tiny chips of metal flow out, your gears are likely grinding against each other. 

Step #7. Fill the engine block with antifreeze

Filling the engine block with antifreeze will prevent residual water from freezing and cracking. A non-toxic propylene glycol antifreeze is best, and your location should determine its strength.

Step #8. Grease gears and fittings

You'll likely locate your engine’s grease fittings in the steering mechanism area. Use a high-quality marine lubricant to protect against rust, corrosion, and oxidation. In addition, the owner’s manual should list other vital areas that need greasing before winter storage.

Step #9. Drain fresh water plumbing systems

Heads, sinks, tanks, and anywhere else, water accumulated during the season must be drained and pumped full with antifreeze to protect them and prevent moisture from gathering as you wait for the next boating season. Additionally, drain the other internal systems like the bilge (remove the plug to prevent moisture build-up in the hull) and raw water washdowns. 

Step #10. Prevent mold and mildew buildup 

The humidity of your boat’s cabin may cause mold and mildew during its time in winter storage. The musty odor aside, mold and mildew can permanently damage upholstery and, worse, lead to respiratory illness in sensitive individuals. Below are some measures to consider:


Ventilate: You can use a device like cowl ventilators, clamshell ventilators, and louvered ventilators or use a shrink wrap ventilators.

Dehumidify: You can reduce humidity with specialty moisture absorbing crystals from Star Brite, Mary Kate, and other manufacturers.

Treat: Or, use chlorine dioxide technology to treat the boat’s cabin during storage or when recommissioning in the spring.

Step #11. Remove valuables

Boatyards rarely see people during the winter, which makes break-ins easy. To prevent your valuables from getting stolen, remove expensive electronics and other costly items from your vessel. In addition, your boat should have insurance, even when it’s not on the water.

Step #12. Remove or disconnect batteries

This is an optional step, but it's wise to remove and charge your batteries while your boat is in storage. In any case, disconnect the cables or move the battery to the offsetting and take any on-marinized electronics indoors. 

Step #13. Cover your boat

Finally, regardless of if your vessel is heading to storage, shield your boat with a durable cover or shrink wrap. 


As the temperatures fall toward freezing, you'll know it's time to winterize your boat to protect it from all the elements. To find the latest information about frost/freeze in your area, visit the National Center for Environmental Information. Though we hate to see the boating season end, this is your chance to ensure your boat is ready for its first spring splash.

We hope you’ve found this guide helpful. When you’re ready to dewinterize you’re boat, check out this blog! If you’re a snowbird or plan to soak up all that’s left of summer, as always, you can rely on Dockwa for your marina boat slip or mooring reservations.


C​​heck out our other blog posts to get an inside look at our favorite destinations, marinas, liveaboards, and tips for boaters. Join the conversation on Flipboard, Facebook, Twitter, and Instagram.

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