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Winterization - Prepare Your Boat For Winter Storage
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Winterizing Engines & Fuel Systems Water SystemsWater Systems Exterior/InteriorExterior/Interior Storage

When the weather turns cool and your boating season begins to wind down, it's time to start thinking about storing your boat for the winter. Preparation for changing weather and proper care of your boat are essential to keeping your vessel running well and making sure it's ready to launch in the spring. Failure to prepare your boat for the winter can lead to unwanted damage and costly repairs. Leaving cylinders unprotected can lead to severe rust; a cooling system that's not been flushed may contain salt crystals that will corrode the cooling passages in the winter. By investing a little time and expense, you can skip the headache of major repairs in the future and enjoy more time on the water. In an effort to help you be better prepared, we're offering these helpful tips for getting your boat ready for the offseason.

Winterizing Engines & Fuel Systems

Winterize your engine to extend the life of your power train and prevent costly repairs from freeze damage. The main tasks to accomplish in winterizing your engine include Cleaning the Fuel and Filters, Adding Antifreeze, Fogging the Engine, and Changing the Engine and Transmission Oil.

Cleaning the Fuel and Filters

First, fill the fuel tank with gas and add a fuel stabilizer. You can check your owner's manual for recommendations or look for your choice here on our website. By filling the tank and reducing the amount of air in it, you also reduce the moisture that forms from condensation. Adding the fuel stabilizer helps keep gum and varnish from building up and clogging fuel lines, carburetors, and fuel injectors. It's also a good time to change the filter element in your fuel filter/water separator.

Adding Antifreeze And Fogging the Engine

Flush the engine with antifreeze to prevent any residual water from freezing and cracking your block by expanding. Choose a non-toxic antifreeze made of propylene glycol to prevent contamination of lakes and waterways.

For outboards and sterndrives, hook up a freshwater hose to a motor flusher and place it over the raw water intake. Turn on the freshwater and start your boat's engine. Allow the engine to warm up so the thermostat will open and let coolant circulate through the entire engine. After warming the engine, turn it off and hook up a winterizing kit to the motor flusher. Remove the flame arrestor from the carburetor so you can add the antifreeze and then fogging oil to the engine. Start the engine again and open the valve to the winterizing kit. You'll see the level of antifreeze in the winterizing tank drop, and you should also begin to see antifreeze come out of the exhaust.

When the tank is almost empty, begin spraying fogging oil into the carburetor. This will probably cause the engine to sputter or stall, but continue running the engine while it emits white smoke. Spray a good amount of fogging oil through the intake, then turn the engine off. Another way to add fogging oil is by removing the spark plugs and spraying the oil directly into each chamber.

Using fogging oil in your engine creates an anticorrosive coating to the interior surfaces of the cylinders. Letting the engine run till it dies burns up all of the fuel in the carburetor and keeps the evaporating gas from forming varnish deposits.

Fogging oil is relatively sticky and could possibly hang up an injector if used in a fuel-injected engine. So instead, if you have an EFI engine, add an ounce of 2-cycle outboard engine oil in the fuel/water separator; then run the engine briefly to coat the internal components.

For inboard engines, the process is a little different. Warm the engine as with the sterndrive. Fill a 5-gallon bucket with non-toxic antifreeze. Close the intake seacock. Remove the intake hose from the seacock and place the end into the antifreeze in the bucket. Start the engine and let it idle until antifreeze discharges from the exhaust for at least 30 seconds. When the bucket is almost empty, begin fogging the carburetor. Continue spraying plenty of fogging oil even as the engine sputters. When the antifreeze runs out, turn the engine off and secure the intake hose back on the seacock.

Changing the Engine and Transmission Oil

Next, while the engine is still warm, change the engine's oil and oil filter. It's best to change the oil now when winterizing, because the old oil contains contaminants and acids that can wear on your engine during the winter lay-up. Removing the old oil while the engine is warm helps to drain away those contaminants with the oil. You should also change the gear oil at this time for similar reasons.

Water Systems


Clean up any oil spills with soap, water, and a stiff brush. Then spray the area with a moisture displacing lubricant. You can also add a little antifreeze to the bilge to keep any water from freezing.

Freshwater System

Completely drain the freshwater system and the water heater. Add non-toxic anti-freeze to water tank and water heater. Pump antifreeze into freshwater supply lines that connect to faucets and transom shower.


Pump out the holding tank at an approved facility. Add freshwater to the bowl and flush several times. Check your owner's manual for recommended cleaners that will not harm your system and follow instructions for use in cleaning out the plumbing system. After using the approved cleaner, add freshwater to the bowl and pump out again. Add non-toxic antifreeze and pump through hoses, holding tank, valves, macerator, and discharge hose. Please check your owner's manual to be sure a non-toxic, alcohol-based antifreeze will not harm your system.


Pressure wash and clean your boat's hull. Clean the barnacles off props, shafts, rudders, struts, and trim tabs. Clean thru-hulls and strainers. Open the seacocks and let any water drain out. This is also a good time to give the hull a wax job.


Check the interior of your boat and remove any valuables, electronics, PFDs, extinguishers, flares, fenders, etc. Use the winter to clean and inspect these items and replace them if necessary. Remove interior cushions, rugs, jump seats, and anything else that might retain water and encourage mildew. Store items in a cool, dry place. Open and clean all drawers, lockers, refrigerator, freezer, etc. To help control the moisture and prevent mildew, you could install a dehumidifier or use a moisture absorber.


Out Of Water

The best place to store your boat during the winter is out of the water in a garage or climate-controlled boat storage facility if possible. You can also consider shrink-wrapping your boat. These options are not always available and can be expensive. So the choice for most boat owners is to cover the boat with a boat cover. Before covering, make sure the interior has been allowed to dry out. Moisture and poor air circulation are the main causes of rot and mildew. So, choose a quality boat cover that breathes, allowing air in while keeping moisture out. Also, consider adding a vent or ventilating fan to your boat cover to aid the air circulation.

A boat cover that is not well supported will accumulate snow and water, adding considerable weight to the boat. Standing water on your boat cover may eventually find it's way to your boat's interior, leading to rot or mildew. Keep water, snow, and debris from sagging in your boat cover and forming water pockets by adding a boat cover support system.

If your boat is being stored on a trailer, you should block the trailer wheels so the tires are off the ground to reduce deterioration to the trailer tires. This also may help to deter theft. It's also a good idea to replace wheel bearings, worn rollers and hardware, and other aging trailer parts when preparing for winter storage.

Store sterndrives in the down position to prevent strain on the exhaust elbows and universal joint bellows.

Bimini tops should be removed, cleaned, repaired if needed, and stored for the winter. This will help keep them from aging prematurely or being damaged by the weight of snow.

In Water

If your boat is staying in the water for the winter, close all seacocks and check rudder shafts and stuffing boxes for leaks. Tighten and repack if necessary. Check all thru-hull fittings above the water line as well. A cracked plastic thru-hull near the waterline could be a disaster if the weight of snow or ice causes the boat to sink a couple of inches. If cracked, replace the thru-hull with a bronze fitting or store the boat out of the water until it can be repaired.

Make sure your battery is fully charged and verify that your charging system is working properly. Check bilge pumps and float switches to make sure they are working properly. Monitor your boat on a regular basis throughout the offseason, at least once or twice a month, checking for leaks or other issues. If your boat is moored in an area that is prone to freezing, suspend a water agitator or de-icer below the boat or from the dock to prevent damage from ice.

Other Systems & Parts To Check When Winterizing

  • Check the exhaust system for carbon build-up or corrosion.
  • Check the raw water injection hose for debris or scale.
  • Check all hoses for bulges or cracks.
  • Check hose clamps for tightness and corrosion.
  • Seal the engine openings to keep out damp air.
  • Inspect motor mounts.
  • Lube all grease points on the engine.
  • Apply water-resistant grease to the propeller shaft and threads.
  • Inspect and lubricate steering and trim.
  • Inspect shift and throttle cables.
  • Unless you need to leave a battery aboard to operate a bilge pump, you should remove all batteries, recharge them, and store in a safe, dry place.


Following some of our suggestions above should help keep your boat safe through the winter and make getting ready to launch in the spring much easier. However, please remember to always consult your owner's manual for recommendations on winterizing. If you are not experienced at winterizing a boat or have questions or doubts, please consult a professional for help in doing the job. As always, happy boating!