Boat winterization

Best practices

Kim Fundingsland/MDN Boat owners should pay particular attention to the lower unit of their outboard motors when winterizing. It is also a good time to check for propeller issues in preparation for the next boating season.

Many boaters and fishermen have put their boats away until next year. Others will be doing so once the weather gets too cold to be on the water. No matter if you’ve already parked your boat for the season or are about to do so, there are some important things to do and check on before winter arrives.

Winterizing a boat can be done by your favorite marine mechanic, but there are a number of things that you can do yourself as well. And don’t forget trailer and tire care. Here’s some advice and tips from boaterinput.com based on a survey of 155 boat owners across the U.S.




If you live in a cold climate with temperatures below freezing, properly winterizing your boat will prevent any residual water in your engine block, drive shaft or gear case from freezing and expanding and severely damaging your engine.


You clearly want to winterize your boat before experiencing freezing temperatures in your area.


The following are the most frequent winterization activities performed by boat owners along with a brief description for why it is important to do each.

Clean Your Boat

It is important to clean your boat inside and out to prevent stains or marine growth from setting in and making it much more difficult to treat later.

Wax Your Boat

After cleaning your boat, it is also a good time to wax it. And, if you store your boat outside (33% keep their boat in their yard or in an outdoors commercial lot), it is especially important since UV Rays will cause fading and oxidation (fiberglass).

Remove Electronics and Stowed Items

Fish Finders, VHF Radios, life jackets, water toys and even removable cushions should ideally be removed before storing your boat for an extended period of time. The most obvious reason is theft prevention. Additionally, mildew, condensation and corrosion could form if the area is not well ventilated.

Top Off the Fuel Tank

There used to be a debate as to whether to empty the tank or fill it up. Now, the matter is largely settled as most advocate filling her up. The reason? Filling the tank does not leave room for condensation which is the cause of most problems.

Add Fuel Stabilizer

Adding fuel stabilizer helps keep your fuel from degrading over the long winter months. Also, you will want a product that treats ethanol if there is the possibility that you have this in your fuel. This is to deter “phase separation” when water separates from the fuel and settles to the bottom of your tank which can be extremely harmful to your engine.

Change the lower

unit gear lube

For most engines, it is recommended that you change your gear lube about every 100 hours or at least once a year. Doing it at the end of the season has the added benefit of ensuring there isn’t any moisture in the gear case that could cause problems in freezing temperatures. If your old gear lube appears white or creamy when changing it, you should take it to a dealer to have it inspected for possible leaks/broken seals. And, when storing your boat, it is important to tilt the engine all the way down (vertical) to drain any water from the lower unit. Otherwise, water could collect and freeze which might bust your gear case.

Change engine

Oil and Filter

If you have an inboard or four-stroke outboard engine, it is recommended that you change your oil and filter approximately every 100 hours, and it is a good practice to do so at the end of the boating season.

According to BoatUS, “residual acids and moisture left in the crankcase over the winter can pit bearings and other vital engine parts.” It is also a good time to change your water-separating fuel filter.

Fog Engine

Fogging the engine provides a protective coating that inhibits corrosion to the cylinders and internal components. It involves spraying “fogging oil” into the carburetor or air intake until smoke is emitted. It is best to also remove each spark plug and spray some additional fogging oil into each cylinder for good measure.

Charge and/or remove batteries

Before putting your boat away for an extended period, it is important to check that your batteries are fully charged. This is because batteries naturally discharge over time.

According to BoatUs, a typical lead-cell battery will lose approximately 5% of its charge per month.

Grease the prop shaft

Another simple but helpful step is to grease your prop shaft. This will prevent rust from forming and “freezing” your prop to the shaft. Simply remove your prop and apply a liberal amount of marine grease before replacing it.

Grease trailer bearings If you trailer your boat, it is important to inspect your bearings periodically to reduce the chances of failure on the road. Trailer manufacturers generally recommend replacing the grease every 3,000 or 4,000 miles or once a year.


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