The Ultimate Checklist for Winterizing Your Boat (Detailed PDF)

More than twenty years ago when I bought my first boat I didn't have a clue about a lot of things. As the first sailing season was winding down, a friend asked me about my plans for "winterizing" the boat.

Huh?

I'm sure my dumb look was priceless. As a new boat owner I'd been more concerned with figuring out which lines went were and how to get in and out of a slip with all my gel coat intact than any thoughts for the winter.

What is winterizing a boat? Winterizing a boat is securing every system on the boat against freezing, corrosion, and damage from cold while preparing the boat for layup and disuse. Systems get drained, flushed and filled with antifreeze, the boat gets covered and protected from snow and ice, and engines and mechanical systems are cleaned, lubricated and stored so they start up again easily in the spring.

Sounds like a lot of work, right? It can be, but it depends on the size of your boat. A large boat with multiple complex systems will take some time, but a simple day sailor with an outboard can be done in an afternoon.

It's not complex, you just need to know what to do for the specific systems on your boat. This is more checklist than a detailed step-by-step guide so you understand what you're getting into and what needs to be done.

You can download a free PDF of the checklist here.

In this article:

  1. Supplies You May Need
  2. The Engine and Generator
  3. Fuel Systems
  4. Plumbing Systems
  5. Refrigeration
  6. The Bilge
  7. Batteries
  8. Air Conditioning
  9. Water Maker
  10. Covering, Ventilation and Moisture
  11. Sails
  12. Store the Boat
  13. Visit Your Boat!

Supplies You May Need

Your specific needs for winterizing will vary with the systems on your boat and the type of engine and fuel you have and the type of storage you choose. Quantities will vary with the size and complexity of your systems.

  • Non-toxic Propylene Glycol antifreeze - the "Pink Stuff" (water systems, engine, bilge) for -50F protection, or -100F for colder climes (usually green or blue). Do not use Ethylene Glycol or auto-anti-freeze for winterizing. It is highly toxic to you and to marine life.
  • Engine oil and filter (engine)
  • Fogging oil (engine)
  • Fuel stabilizer/biocide (engine)
  • Antifreeze Hydrometer or "antifreeze tester." (engine)
  • A cover - shrink wrap, tarps, a canvas cover, or indoor storage
  • Dehumidifying agent or dehumidifier/heater (cabin)

The Engine and Generator

The task for all engines is similar, though the specific steps vary.

  • Rinse and flush the engine with freshwater to remove salt.
  • "Fog" the engine with a spray oil.
  • Flush antifreeze through the engine.
  • Change the oil and oil filter.
  • Change fuel filters.
  • Close through hulls on intakes and fill strainers with antifreeze.

Inboard Engines

Freshwater cooled inboard engines have a few more steps for safety.

  • Check antifreeze level in the engine block with a tester and add anti-freeze as needed to maximize cold protection. Make sure you circulate the new mix before re-testing.
  • Flush and fill the engine and lines with antifreeze.

Outboards

  • With the engine running, disconnect the fuel line and run the engine until it stops. This empties all the fuel from the carburetor.
  • Change lower unit oil.

Learn more about what happens to your engine if you don't winterize your boat here

Fuel Systems

Diesel Fuel

  • Add a biocide/stabilizer to the fuel tank.
  • Fill the tank after you add the stabilizer.

Gasoline

  • Most gasoline outboards use a removable tank. This fuel should be disposed of properly or used for some other purpose so you start with a fresh tank in the spring. (I used to put my leftover dinghy fuel into my car.)

  • If you have an older boat with a gasoline inboard and permanent tank installed you can drain it, or add a stabilizer and fill it.

Plumbing Systems

Pressure (Fresh) Water

  • Flush all tanks and lines.
  • Add antifreeze to the water tank.
  • Run all fixtures until antifreeze runs out, starting with the fixtures farthest from the pump.

Water Heaters

  • Drain all water.
  • If there is a winterizing bypass, shut it off before winterizing the pressure water system so you don't have to fill the tank with expensive antifreeze.
  • Disconnect the electricity or turn off the breaker to prevent accidental startup in the spring while it's empty.

Heads and Toilets

  • Flush all toilets with fresh water
  • Pump out and rinse all holding tanks.
  • Using the water intake hose, flush the system through with antifreeze

Refrigeration

  • Flush all raw water lines with antifreeze

The Bilge

  • Pump or drain the bilge into a proper receptacle.
  • Add antifreeze to cover exposed pumps or through hulls
  • Run the pump briefly fill it with antifreeze.

Batteries

Most boats in seasonal cruising regions are still using Lead-Acid batteries - either flooded (wet) cells, AGM, or Gel. There are minimal differences between lead-acid types when winterizing, but LiFePO~4~ banks require different long term layup care.

Lead-Acid

  • For wet cells, top up all cells as per manufacturer's instructions (usually with distilled water).
  • Fully charge all batteries.
  • Disconnect electrical connections from the boat.
  • If practical for smaller batteries, remove them and store indoors with a trickle charger.

Lithium (LiFePO~4~)

Consult your manuals for details on longer term layup instructions and periods of disuse. LiFePO~4~ technology is fairly new and manufacturer recommendations should be followed when available.

  • Charge/Discharge to 50% state of charge or manufacturer's recommended storage voltage.
  • Disconnect all connections from the boat.

Air Conditioning

  • Flush and fill raw water lines with antifreeze.

Water Maker

Be sure to read the manual and follow all steps in order. Sending pressurized antifreeze through your membrane can damage it.

  • Pickle membrane with preservative as per manufacturer's instructions.
  • Flush raw water intake systems with antifreeze.
  • Replace or remove all filters.

Covering, Ventilation and Moisture

Boat Covers

Boats stored outdoors in places with freezing temperatures should be covered. While a detailed discussion about boat covering and types of covers is beyond this article, you should be aware there are multiple options.

  • Canvas Covers. Expensive up front, but reusable from season to season and the best environmentally and for the boat.
  • Shrink wrapping. An annual expense that you may want to leave to the pros to do. Should be recycled in the spring.
  • Tarps and improvised materials. Smaller boats can be covered with tarps and other inexpensive materials, but they are prone to blowing off and coming loose. Tarps are difficult to secure on wet-stored boats since you can’t get lines under the hull easily.

Ventilation and Moisture

Stagnant air and trapped moisture is a leading cause of mold and mildew growth over boats in the winter.

  • Make sure any boat covers have leak-proof ventilation and allow airflow.
  • Open all cabinets and storage areas, empty lockers where airflow is restricted.
  • Remove mildew prone items such as towels and clothing for the season and store off the boat.
  • Consider chemical desiccants, a fan, a winter cabin heater and/or a dehumidifier.
  • If security permits, leave some windows or a hatch open under the cover.

Sails

  • Rinse and sails with fresh water and allow to dry prior to flaking.
  • Take any sails in need of repairs to a sail loft.
  • Consider annual inspection, cleaning and winter storage with a sailmaker to extend sail life.

Store the Boat

You must make arrangements well in advance for a place to store the boat for the winter. Considerations of budget, local climate, and geography will drive this, and each storage method has advantages and disadvantages.

Hard Stands/Dry Storage

Dry storage is the most common in colder areas where salt water may freeze. Your boat can't sink on the hard, and it will be available to work on, though you'll need a ladder.

Taking the rig down for the winter is usually not required, but it will afford the opportunity to inspect and service the rig in the off season and reduces windage if you store in a storm prone area.

In-water Storage

In-water storage is a good budget alternative, but it needs different steps.

  • Keep bilge connected to a battery.
  • Keep batteries charged for bilge pumps.
  • You may want "Ice Eaters" in the slipe for areas prone to freezing.

Trailer

Trailered boats are easy and cheap to store if you've got space. Be sure to still cover the boat and winterize systems unless you're storing it indoors.

Indoor Storage

Indoor storage removes the need for a cover, but will usually require mast removal. Take care to still winterize systems if your storage building is not heated.

Visit Your Boat!

"Out of sight, out of mind" is a common problem with winter storage. Except for violent storms, most winter storage damage doesn't happen quickly. It's the result of creeping effects, like water seeping in and freezing, mold growing in damp, stagnant spaces, or heavy weights of snow and ice pressing on covers and breaking them.

So make the time in the winter to check your boat now and then. After a snow or big freezing rain storm check for accumulation on the cover and leaks and incursions. Nip problems in the bud. When you open up a clean boat that smells nice in the spring you'll forget that cold day in February when you swept the snow off the shrink-wrap.

The best prevention in the fall won't help you if something goes wrong and unchecked for the rest of the winter.

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