When autumn leaves adorn the trees and you have yet to put away your flip flops, it’s hard to imagine that soon you'll have to start thinking about winterization procedures for your boat. It’s even harder to envision next spring. But if you’re going to do what’s right for your boat, you need to look to the future. Think about winter as an immediate concern. If you winterize your boat well now, your boat launch in May 2021 will go more smoothly.

If you winterize your boat properly now, launching in the spring will go much more smoothly.

Ask any boatyard manager what he or she has seen in winters past, and what you hear will make you cringe: boats sinking under the weight of snow or due to open seacocks and valves, boats left under cheap tarps that get torn in nor’easters and end in tatters, and boats neglected all winter by their owners. It’s critical to learn how smart owners avoid the most common mistakes.

Here are winterization factors to consider: 

Where to store your boat? 

Many unfortunate boaters who have experienced their boats sinking over the winter have one thing in common: they have failed to protect the thru-hulls by closing the seacocks and gate valves. 

According to BoatU.S.: “All thru-hulls, especially the ones for the cockpit drains, must be doubleclamped with stainless steel hose clamps at each end. When water freezes, it expands and will lift a poorly secured hose off of a fitting. The hose itself is also important. Lightweight hose and PVC tubing can rupture or crack. Use only a heavily reinforced hose, especially at cockpit drains.”

Although it’s the safest bet for not sinking your boat, storing her ashore adds extra exposure and vulnerability to cold air. Your hull will develop fewer blisters than one left in the water, yet your engine and freshwater systems will get colder faster. It’s important to winterize them.

When engines run, they are “happiest.”

Taking care of your engine

When engines run, they are “happiest.” Engines that sit idle in frigid temperatures are headed for trouble. Many insurance policies do not cover frozen or cracked engine blocks, so this is important. If your owner’s manual includes winterization procedures, follow those.

For most engines, other than your regular lubricants, you will need an aerosol can of fogging oil, a fuel stabilizer (gasoline engines) or a fuel biocide (diesel engines), and for inboards, a gallon or two of non-toxic propylene glycol antifreeze (the pink, not green stuff). The basic procedure for most engines is to flush with freshwater, empty fuel lines and carburetors, fog the cylinders, and lubricate. For a detailed checklist, visit proptalk.com/winterization-tips-and-winter-storage for links to engine winterization procedures.

Take it off!

To discourage theft, dismount electronics and take them and any other valuables home for safekeeping during those winter months during which your marina can be too quiet.

Remove from the boat anything that’s scary to light a match to: cooking fuels, charcoal, coatings, and paint thinners. Don’t leave propane canisters lying around, as they may rust or leak. Leave one functioning fire extinguisher within reach. While you are checking that off your list, check its charging status and the expiration date on your flares.

Some people like to remove their cushions from the boat; others advise leaving them propped up at odd angles to the furniture to let air circulate and fend off mildew growth. If you leave sheets or towels on the boat, putting air freshener sheets in between them keeps them fresher.

Take off all canned foods or bottled drinks. They can freeze, which may break their seals and cause a huge mess.

Covering your boat

Over the years, many marina managers have told us how many boats they have seen decay because their owners chose cheap tarps as winter storage covers. Your gel coat and boat overall will thank you if you invest in a good synthetic, or even better, a longer-lasting canvas cover. Frame up the cover to allow circulation and prevent water pooling.

Another option, and a very good one if well-vented, is to shrink wrap your boat. Make sure to recycle the wrap in the spring, if your marina provides this option .

Although the bimini makes a terrific July sunshade, do not expect it to protect your boat from freezing rain and snow; it’s best stowed below or in a dry place on land. Winter is a great season to have biminis cleaned.

Don't forget to check on your boat regularly. 

Check on your boat regularly

Visit your boat at least once a month during the winter, especially before and after harsh weather, or ask a friend or marina manager to check on her. In the spring, when it’s time to get the boat back in the water, she will thank you.

Check out this checklist

Find BoatUS’s free and extensive online resources at boatus.com/winterization. As well as winter layup checklists and a downloadable “Boaters Guide to Winterizing,” you’ll find tips on onboard plug-in heaters, what to do if there’s E10 fuel in your tank, winter storm prep, and more. 

Also note that many full-service marinas offer decommissioning checklists and other resources on their websites. If you do your own engine winterization, make sure to consult the manual for your particular engine. 

What happens to water when it freezes?

“If you’ve ever seen the picture of a water molecule, it looks like a Mickey Mouse head with an oxygen molecule where Mickey Mouse’s face is, and then two hydrogen atoms where his ears are. The oxygen atom is slightly negative, and the hydrogens are slightly positively charged, so water molecules tend to stick together forming what are called hydrogen bonds.

“Because of that shape of the molecule, the way water molecules tend to link together is actually a very open structure with big holes. There’s a lot of extra ‘empty’ space. When water freezes, it releases energy because a lot of extra strong bonds can be made. It does take up more space. And so, ice expands when it freezes.” (from the University of Cambridge’s thenakedscientists.com)

After analyzing 10 years of freeze claims, BoatU.S. Marine Insurance found that more than three quarters of claims involved cracks in the engine block or the exhaust manifolds that occurred because water remained in the engine or cooling system during a hard freeze. You must drain water out of your engine in winter. See your engine owner’s manual or consult a professional to learn how.

Green winterization tips:

  • Use less toxic propylene glycol antifreeze.
  • If practical, capture any antifreeze in a bucket when flushing to prevent overboard discharges.
  • When performing engine work, place an oil-only absorbent pad under the area to catch drips or small spills.
  • Use small containers of oil and other hazardous cleaners; small containers mean smaller spills.
  • Keep containers near the center of the boat to minimize the chance of an overboard spill.
  • Temporarily plug all scuppers and drains and disable your bilge pump while performing maintenance. (Be sure to turn the bilge pump back on when finished.)
  • Look for used oil and antifreeze recycling at your marina and dispose of hazardous wastes properly. 
  • Visit earth911.org to learn about local waste disposal.

Courtesy of BoatU.S. Find more at boatus.com/winterization.