To winterize in the north, protect from freezing every place where water can collect; service the engine; and prevent moisture, snow, and ice damage. It’s best to do the engine and holding tank work before haul-out, then finish the hull, deck and interior ashore.
Fill the diesel tank nearly full after first adding a diesel fuel stabilizer, if using one, and then run the engine long enough to reach operating temperature. While the engine is still warm, change the oil and oil filter. Change the transmission fluid, if due, and the crankcase breather filter, if fitted.
Three separate systems on a boat have antifreeze:
- The closed engine cooling system containing engine antifreeze filled from a cap on top of the engine.
- The raw water cooling system that pumps seawater through the heat exchanger and out the transom exhaust port.
- The drinking water system that carries potable water from the tanks to sinks and showers.
Each takes a different type of antifreeze. Only the raw water system and the drinking water system need to be winterized.
Seawater cooling system: Follow the engine manual procedure to drain the raw water cooling system. Typically: Warm up the engine and turn it off, then disconnect the raw water pump intake hose at the strainer. Immerse the hose in a large bucket of plain water and run the engine briefly to flush out salt. Keep refilling the bucket and do not let it run dry. After stopping the engine, empty the bucket and fill it with marine engine antifreeze rated for the lowest expected temperature. Run the engine until antifreeze comes from the transom exhaust, but again, do not let it empty the bucket.
Use propylene glycol antifreeze that is far less toxic than ethylene glycol. The package should say something like, “Marine engine antifreeze; corrosion inhibited; protects copper, brass, aluminum and solder.” Avoid the bright pink alcohol-based antifreeze used in potable drinking water systems, if possible, because it is weaker, does not inhibit corrosion, can evaporate, and can dry out seals. Do not mix different brands of antifreeze, regardless of color, because they might have incompatible additives.
All glycol antifreeze is toxic and must never go into the water or onto the ground. It has a sweet flavor that attracts animals. Since anything put into the raw water system must eventually come out the exhaust port, many boatyards winterize only with bright pink, alcohol based, potable water antifreeze. It protects from freezing but does not inhibit corrosion.
Drinking water system: Drain the water tank(s) as empty as possible. Switch off the hot water heater at the main panel and drain it. Install a bypass hose between its input and output so you can leave the tank empty. Never power on an empty hot water tank, as this will quickly burn out the heating element.
Remove the hose that draws water in at the water pump and attach a short length of similar hose. Place the other end of that in a bucket of bright pink potable water antifreeze—the alcohol based RV type, not engine antifreeze—and then run each hot and cold sink faucet and shower faucet, in turn, until antifreeze comes out. Do the hot and cold sides separately starting with the fixtures nearest the pump.
If you have compressed air, instead open the water pump outlet hose and blow air through it while opening each faucet, in turn, until no water comes out. Although there might still be water in low spots, almost always it is in hoses that can expand when the water freezes. If there are instead low spots in solid pipes, use enough antifreeze to reach them.
There is no need to put antifreeze in the nearly empty water tanks. They have plenty of room for ice to expand. Any antifreeze in there will be hard to remove in the spring and will leave an unpleasant taste. Attend, instead, to sink sprayers, shower hoses, and any low points that the water moves through.
Engine: Some sailors remove the seawater pump impeller over the winter so it does not take on a permanent set. If you do, put a conspicuous tag at the ignition panel, or on the engine key, so the engine will not be started without reinstalling the impeller. Inspect the heat exchanger zinc, engine belts and their tension, exhaust mixing elbow, engine coolant level, and engine mounts.
Sanitation system: Before haul-out, pump the holding tank, fill it with fresh water through a toilet, and pump it again. Drain each toilet; their intake and discharge hoses; and the holding tank, macerator, and discharge plumbing. Do not rely on pouring antifreeze only into a toilet bowl, as that alone will not protect the pump and intake hose.
Commonly forgotten items that need to be drained include the anchor washdown pump, refrigerator if seawater cooled, drinking water filter, galley sink foot pump, and deck hoses. A water maker requires its manufacturer’s special storage or “pickling” procedure—ordinary antifreeze might damage some membranes.
Bilge and scuppers: Do not simply pour antifreeze into a dirty bilge. It becomes diluted, could get pumped overboard, and might hide leaks. Pump out the bilge and sponge it dry, then clean up any oil or debris. Clear out cockpit drains, scuppers and deck drains.
Batteries: Fully charge the batteries. Clean and tighten their terminals. Use distilled water to top off the electrolyte level in serviceable flooded batteries. Disconnect parasitic loads. Remove the batteries to a dry place ashore or else leave them aboard only if AC power for the battery charger—or a solar panel—is available. Either way, keep them trickle charged so that the electrolyte does not freeze.
Lithium batteries are different. Most must never be charged when cold. Charge it to the manufacturer’s recommended level for storage, commonly around 50–60%, although some brands instead recommend fully charged storage. Disconnect it at the positive terminal. Some LiFePO4 battery management systems draw a little power even when disconnected, so turn that BMS off if it has a switch.
Although they can be stored without charging well below freezing, charging below the lithium battery maker’s temperature limit—often 32°F, and up to 41°F for some—can permanently damage the cells.
Disconnect shore power unless the yard specifically allows it. Remove dry cell batteries from flashlights, remotes and handheld instruments.
Sails and canvas: Handling loose sails is like herding cats: difficult until you have bagged them. After removing any battens, fold a sail by laying it out along the dock and then, starting with the luff, smooth a few feet and fold it over. It is easier having a helper with one at each end. Next, working from one end of the long roll you just made, fold the sail into a bag-size bundle and secure it with a tie. Do not bag or even fold sails while they are wet. Wash salt off and have tears, loose stitching and UV covers repaired as needed. Most sailmaker lofts will store any sails that they clean or service at no charge.
Above deck: Tie halyards away from the mast to prevent slapping. Inspect turnbuckles, their cotter pins and the lifelines. Seal—but do not permanently block—any openings where rain can enter. If the mast is unstepped, this is a good time for a close inspection of the standing rigging, masthead sheaves, above deck lights and their wiring, spreader roots, the boom gooseneck, and chainplates.
Remove or firmly secure the anchor and any loose deck gear. Drain and clean the anchor locker. Remove dock lines and fenders unless they will be needed. Lubricate winches if due. Ensure that propane cylinders are shut off and consider removing them to storage ashore. They probably need to be refilled, anyhow.
Hull and propeller: Pressure wash the bottom immediately after haul-out, before marine growth dries hard. Most boatyards do this routinely. Inspect the hull for blisters, cracks and grounding damage. Inspect the propeller, shaft (check for play), strut, cutless bearing (check for wear) and the stuffing box or shaft seal. Replace any badly used-up zinc. Note the brand, or at least the type, of bottom paint so that a new coat in the spring will match it.
Below deck: Remove anything that can mildew, freeze, attract rodents or become damaged. This includes all food and beverages including canned goods, cleaning liquids, medicines, paper products, bedding, and clothing.
After cleaning the refrigerator and freezer, dry them well and leave their doors propped open. Also leave cracked open all lockers, drawers and access panels. Stand any remaining cushions on edge.
Covering the boat: A proper winter cover should be strongly supported so it cannot collect snow or water and should have a ridge high enough to shed snow. It should be padded wherever it contacts stanchions or pointy fittings. Tie it only to the cover framework or cradle, not to the jack stands because in high wind that cover might become a sail. Allow ventilation at both ends. Leave access to come aboard during the winter.
Shrink-wrap works well if it has adequate vents and access doors. A reusable fitted cover is usually better than shrink wrap over many seasons but it needs a well-designed frame. Do not tie the cover down in such a way that high wind could pull out a jack stand.
Blocking ashore: The boatyard normally handles blocking, but confirm that the keel carries most of the boat’s weight. Jack stands should stabilize and balance the hull, rather than supporting it. They should be chained together and have pads that bear against structurally sound portions of the hull. Do not adjust boatyard jack stands yourself without permission. Blocked boats can topple like dominoes.
Visit the boat after the first strong wind, the first heavy rain and every major snowstorm. Most winter damage comes from a loosened cover, blocked drain, dead battery, shifted jack stand or unnoticed water intrusion.
Bubblers and de-icers: A winter dock de-icer protects pilings and boats kept at the dock from thick ice that can shift or lift pilings and damage hulls. There are two types. Propeller de-icers have a submersible motor that sends warmer bottom water up to the surface in a strong, directed flow. They might be less effective in shallow water or extreme cold. Air bubblers have a dock mounted compressor that sends air through perforated tubes. They are best for long, narrow areas like docks, and they keep electrical cords out of the water.
Hang a propeller de-icer slightly below keel depth but well above any mud or weeds on the bottom that might clog it. Use a rope, not the electrical cord. Aim it toward the boat and especially the rudder without letting it direct a steady stream at one part of the hull, which can cause blisters.
Notify the marina or harbormaster and check local rules. Creating open water can lead to liability and might be regulated. Plug the unit into a GFCI circuit to avoid electrocuting a diver.