Boat Winterizing

By Bob Adriance

While the entire crew is likely to lend a hand for spring fitting out, reversing the process in the fall is like cleaning up after a party; there are few volunteers and even less effort.

True story: A man in Minnesota was planning to spend the weekend hunting. As he was heading out the door with his buddies, his wife asked when he was going to winterize his boat. The man put his arm around her and said, "Honey, I think of it as our boat. Would you do it?" So she drove to the boat, poured kerosene in the bilge, and tossed in a match.

Two points: The wife's winterizing "shortcut" created more problems than it solved, and the couple is no longer married. BoatUS didn't insure the boat, incidentally. This incident wasn't the first time a boat was damaged by a hasty winterizing effort. Many boats are damaged or even destroyed every year because the systems aren't given the attention they deserve. While everybody knows that the engine and freshwater system must be winterized, there are many small but critical jobs that should be done that tend to go begging. Here are various winterizing chores that are most likely to be overlooked.

Did you drain the engine intake sea strainer? Everyone knows to winterize the engine, but not everyone knows to drain the sea strainer. Water left in the strainer can freeze and break the watertight seal. When that happens, water is free to enter the boat in the spring when the ice thaws and the intake seacock is opened.

Have biminis and dodgers been stored inside? There's a common misconception that a cover that protects the crew from sunlight and spray will also protect the boat from freezing rain and snow. Quite the contrary, biminis and dodgers tend to be ripped apart or, more likely, aged prematurely by the effects of winter weather while doing almost nothing to protect the boat. Aluminum support frames are frequently bent by the weight of accumulated snow. Biminis and dodgers should be taken home for the winter, cleaned, and, if necessary, re-stitched and repaired.

Photo in frozen water by a dock in danger of sinkingBecause they can sink, boats are safer over the winter when they are stored ashore. This is especially true of boats with large open cockpits and low transoms.

If the boat is stored in the water, did you close all of the seacocks? If you leave your boat in the water over the winter, it's absolutely essential that you close the seacocks. Leaving a boat's seacocks open is like going on an extended vacation and leaving the doors to your house unlocked. Neglecting to "lock" even one door is significant risk. If a thru-hull below the waterline can't be closed, either because it is broken or mechanically frozen, the boat should be stored ashore for the winter. The sole exception is cockpit drains, which must be left open to prevent water accumulations in the cockpit. These should be inspected to ensure that the hose and the hose clamps (two at each connection) are in good shape.

How about the thru-hull fittings above the waterline? While boats with low freeboard are more likely to be overcome by rainwater or a slow leak, a boat is often much "closer" to the water than its freeboard would indicate. A cracked plastic thru-hull at the boot stripe means that the boat only has to sink an inch or two before it floods and heads to the bottom. Boats have sunk because cracked thru-hulls near the waterline were submerged by the weight of snow and ice in the cockpit. Plastic thru-hull fittings deteriorate in sunlight and should be replaced with bronze if they are cracked or broken. If this can't be done immediately, the boat should be stored ashore.

Did you add extra lines and chafe protection? Blustery winter winds never should be confused with gentle summer breezes. All it takes is one good winter storm to abrade a dock line and maybe bash a hole in the hull. If the boat is left in the water, double up on dock lines, and this is a good idea all year add chafe protection.

Is the boat covered properly? A bona fide winter cover is terrific protection if it's adequately ventilated. With most boats, lack of ventilation beneath the cover causes mildew or even rot problems below. If the boat has been painted with two-part polyurethane paint (Imron, Awlgrip are two examples), lack of ventilation can cause tiny blisters in the paint. The problem occurs most often when shrinkwrap covers aren't ventilated, but the blisters have also appeared when a poly tarp sags against the paint, trapping moisture against the surface. Any cover that isn't well-supported will accumulate snow and water, which adds considerable weight to the boat.

Are the cockpit drains clear? Many boats are damaged and even sunk by nothing more than a few leaves blocking cockpit drains. Water trickles through the companionway, stains the interior woodwork, delaminates the cabin sole, and soaks into bulkheads, leaving open the possibility that rot will rear its ugly head sometime later. In one instance, water trickled through the keel bolts, which then froze, and pulled the keel away from the boat's hull.

Photo of 22-foot sailboat that sank when its scuppers were shoved below the waterline by the weight of a winter snowThis 22-foot sailboat sank when its scuppers were shoved below the waterline by the weight of a winter snow. Water poured into the cockpit and found its way through the companionway into the cabin.

Have you taken electronics and other valuables home for the winter? Most marinas are like ghost towns in the winter, with little or no security, which makes stored boats an easy target for thieves. Electronics and other valuables (tools are a popular theft item) should be taken home for safekeeping. Finally, no matter how well it's secured at the marina, a dinghy will always be safer in your garage or backyard.

If the boat is stored ashore, is it supported properly? Lysle Gray, boating sage and the retired president of the American Boat and Yacht Council, noted that almost as many boats are damaged ashore by improper blocking, as are damaged in the water. A few of the boats are toppled over by wind, but many more are damaged slowly, plagued with problems like broken stringers and loose tabbing at the bulkheads.

Most boatyards do a competent job of positioning supports, but it never hurts to discuss technique with the yard manager. With jackstands, the stand should be perpendicular to the hull so it directs the boat's weight toward the ground. Misalignment of the stand will force it out as the load is applied. Even if the stand is aligned perfectly, safety chains must be used between the stands on each side to keep them from slipping out from under the hull. The jackstands should be placed as far out from the boat as practical to support the boat in high winds, with at least three per side for boats over 26 feet and additional supports at long overhangs. Plywood should be placed under each base to prevent it from sinking into mud, sand, or asphalt. Even when stands rest on clay that seems brick hard, they can be loosened by heavy spring rains, shift, and spill the boat.

While jackstands should be placed near bulkheads and beneath the engine, most of the boat's weight rests on its keel. Some boats have specific requirements for support of the keel, but at least one manufacturer warns against putting weight on the keel. If the marina manager isn't familiar with your boat, check your manual or contact the manufacturer.

Keels must be supported by wide, thick timbers the wider the better to distribute the load. Cinder blocks are prone to breaking and should not be used. On powerboats, additional support is sometimes recommended for inboard engines, fuel tanks, and heavy machinery. With outboard and outdrive boats, weight should be taken off the transom by lowering the drive units onto a block.

After the boat is blocked, look along the hull and keel to make sure the jackstands aren't depressing the hull. (Check again in two weeks, after the boat has had time to settle.) The deck must also be level or water could pool and cause stains, mildew, or gelcoat crazing. Finally, never secure the boat's winter cover to the jackstands or support blocks.

Is the boat stored on a trailer? According to the BoatUS Marine Insurance claim files, a boat on a trailer is twice as likely to be stolen as a boat in the water. Thieves are partial to personal watercraft, which are five times more likely to be stolen than other types of boats. If the boat is in your driveway, make sure the tongue is facing away from the street. Another suggestion: Take the wheels off. Besides discouraging theft, storing tires indoors protects them from sunlight and extends their useful life. 

Bob Adriance is the former editor of Seaworthy, the BoatUS Marine Insurance publication dedicated to helping members to avoid injury and boat damage due to accidents and storms. For an insurance quote, please call 800-283-2883 or go to

— Published: October/November 2012

More Reminders

  • Outriggers stored at a 45-degree angle are prone to bending in ice storms. Outriggers should be disassembled or, if that's not possible, stored vertically.
  • Take home cushions, rugs, clothing, and anything else that retains moisture and encourages mildew. Open up locker doors to circulate air down below.
  • Unless you’ll need to leave one aboard to operate a bilge pump, all batteries should be taken home, recharged, and stored for the winter.
  • Plan on visiting your boat regularly, at least once or twice a month. All too often, skippers rely on bilge pumps to bail them out when they're away. The pump fails, the boat sinks. If you can't visit your boat frequently, consider using a buddy system with other boat owners. Another alternative is to ask your marina manger to keep an eye on the boat. Many marinas will inspect boats, usually for a fee.


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