Tech Wiki

Ron Hill, Apache

How to winterize a boat?

Drain the water tanks as much as practicable, then dump two gallons of nontoxic antifreeze into each of them. Operate the cold water faucets in the galley and head until the stream turns red, then shut down the water pump. Open the drain at the bottom of the water heater and let the heater drain completely (make sure that the HOT water faucets are fully open when you do this). There will still be a bit of fresh water in the hot water lines; you can detach the hot water hose at each faucet and blow it out easily. Drop some nontoxic antifreeze into the ice chest so that the drain is flushed. Empty your holding tank as completely as you can, then drop a gallon of nontoxic antifreeze into the head and pump it through until it's gone. Detach the seawater inlet hose from the pump on the head.

For the engine, mix a gallon of nontoxic antifreeze (propylene glycol) with a gallon of water. Detach the raw water intake line, and place it into the bucket containing the antifreeze solution. Start the engine and run it for a minute or so until you see traces of pink from the antifreeze in the water being ejected from the exhaust, then shut the engine down.

Please note that it's illegal to discharge toxic automotive antifreeze (ethylene glycol) into coastal waters [ed].

After the boat is hauled (and this is VERY important!) open every through-hull, and make sure that any intake strainer is opened and drained. The objective is to be sure that there is no plain water trapped inside any plastic housing; if you don't do this, the water will freeze, expand, and crack it!


  1. Be sure your batteries are fully charged and the cells are filled with distilled water, then disconnect the cables attached to the batteries and leave them in the boat. A fully charged battery will NOT be damaged by the cold, and will do just fine where it is; NO need to remove it.
  2. Be sure your fuel tank is filled as much as practicable, and add the appropriate amount of fuel conditioner. Filling the tank helps to minimize condensation.
  3. Empty your bilge, and drop a half gallon of nontoxic antifreeze into it. If you have a keel-stepped mast, or if there's a leak somewhere, your bilge may fill with some water over the winter and might even freeze.... if it does, don't panic; the bilge has sloping sides and even if it freezes, expansion won't crack anything. Mine used to fill and freeze regularly without any damage (Norm Bernstein).

More winterization tips

A few important items that tend to be overlooked:

  • Transmission--Always fill the transmission completely full of fluid (DEXRON III). Over extended periods of non use, the forward transmission to engine seal, because the angle is high, tends to dry out. Filling all the way (takes a quart over the normal level) will keep it moist. Before the transmission can be used, REMEMBER to remove the extra fluid. I've found the easiest way is to suck it all out and refill to its normal level. To replace the forward seal on the Hurth transmission requires removing the engine, as the transmission is bolted to the engine bell housing from the INSIDE! An ounce of prevention is worth a pound of cure.
  • Blocking: To keep the hull from separating from the forward keel (Nov 1990 Mainsheet), insure that more weight (force) is on the forward end of the keel than on the aft end. Because of the weight of a full fuel tank plus the weight of the engine, the stern is naturally heavier and tends to rotate down, lifting the bow. The 5600 pounds of lead wing keel isn't about to be lifted by the bow, hence keel/hull separation. I always block the forward portion of the wing and keep the aft jack stands tightly cinched to keep as much weight as possible on nose of the wing keel.
  • Scuppers: Add a little of the same engine non-toxic antifreeze (propylene glycol) to the scupper drains. If the boat is uncovered in freezing weather, this may be an ongoing process.
  • Bilges: The bilges of keel stepped masts tend to fill with rain water that wicks down the upper spinnaker halyard entrance to the inside of the mast. If the boat is hauled and up for the winter, make sure the bilge pump float switch fuse is removed, as freezing weather could stick the float in the up position, draining the batteries. While hauled, I regularly take a sponge (using rubber gloves because the water is COLD!) and empty the bilge during freezing weather. If in the water, the only solution is to add a little antifreeze periodically to the bilge to keep things from freezing solid.
  • Hidden places: The manual bilge pump drain should be siphoned as dry as possible and add some antifreeze. Also look inside the hull under and aft of the rear berth. There's a scag indentation that collects water on the inside of the hull just forward of the rudder. Empty that area.
  • Rudder: Check the rudder column for water as mentioned in the Mainsheet Feb 1992, Aug 1996 and May 1997.

NOTE: If your boat is hauled and placed in the factory cradle, make sure the yard doesn't put it in there backwards.