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Winterizing your boat is an important step to protect it over the winter and help ensure its longevity. But knowing what's involved will help you make sure it gets done properly and save you from costly repairs in the future.

It includes protecting the engine and other components from freezing and performing other tasks to prevent unnecessary wear or damage due to prolonged storage over the winter.

It's not maintenance. It's just that late Fall is also a good time to perform many maintenance tasks (oil changes, etc.) that for many boat owners should occur annually due to the amount their boat is used throughout the year.

For many, combining winterization and annual maintenance is a convenient way to get it all done at the same time, particularly when hiring someone else to do the work. But regardless of whether you hire someone or DIY, knowing what's involved in each is important.

THIS IS THE MOST IMPORTANT STEP OF WINTERIZATION!! All marine engines use water in some way to cool themselves when they are running. And this water remains in the engine indefinitely after the engine is turned off (except for outboards, see below). If temperatures drop below freezing for an extended period of time (think overnight, particularly when in the 20's F or below), then there is a high risk of this water freezing while inside the engine. As water freezes, it expands, causing everything surrounding it to expand as well. This will in turn rupture hoses and at the worst crack metal parts of the engine, leading to costly repairs. If the main block of the engine were to freeze and crack, the repair bill would likely be in the $ thousands. Not good!

All marine engines have procedures for draining the engine during winterization. This typically involves disconnecting 1-2 hoses, removing 3-4 plugs, etc. It's a very simple job assuming access to these hoses and plugs is convenient. And even when they are hard to reach, there are things you can do as a DIY project once at the beginning to make this ongoing job much easier. See the Time Savers article to read more about those things.

This part of the winterization process takes me less than 10 minutes. And knowing how to do it myself and quickly allows me to use my boat throughout the winter on warmer days, which is good for the boat. BOATS LIKE TO BE DRIVEN, NOT SIT FOR MONTHS WITHOUT USE.

Fuel that sits for long periods of time can go stale. This is particularly true for fuel that has ethanol in it (I strongly recommend that you use ethanol-free fuel in your boat). It is also true when the fuel tank is not completely full (recommended) or completely empty (less practical). That's because the air within the fuel tank will condense with the daily ups and downs of the temperature throughout the winter. This leads to water in the fuel tank and a very poorly running engine in the Spring.

At the end of the season, or any time the boat expected to sit unused for several weeks, it's a good idea to fill the tank completely up with ethanol-free gas and then add a bottle of Sea Foam or Stabil (or equivalent) to help keep the fuel fresh at all times. Here are links to a few good fuel treatment products that are handy to keep on hand (and cheaper than buying at the marina!)...

Sea Foam Motor Treatment16-oz 2-Pack

https://amzn.to/3MkqBGy

STA-BIL 360 Marine Fuel Stabilizer 1-gallon

https://amzn.to/3nULRZU

Batteries also do not like to sit unused for long periods of time. Most marine batteries will lose their charge over the course of a few months, even if they were disconnected. And many boats manufactured in the past10-20 years have some sort of automatic bilge draining system that checks for water in the bilge and runs the bilde pumps when needed to keep the bilge dry. In these cases, batteries may only last for 3-4 weeks before discharging. And discharged batteries are much more prone to freezing and being damaged beyond repair.

So, you have two choices for protecting your batteries over the winter. Either remove them from the boat and store them somewhere dry and above freezing, and either keeping them connected to a trickle charger all the time or charging them periodically.

Or a much more convenient option without too much up-front investment is to install an onboard charger. These chargers cost $50-200 depending on number of batteries to be charged and the charger's features, and they are very easy to install yourself. And using an onboard charger will mean that your batteries will always be in tip-top shape every time you go to use your boat, which also helps to prolong the life of your batteries. Here are a few links to onboard chargers that I have installed and used in my own and friends' boats...

NOCO Genius Gen5x2 10-amp 2-Bank Charger

https://amzn.to/3O4baU4

Pro-Mariner Pro-Sport 12-amp 2-Bank Charger

https://amzn.to/44QlpBz

Those links are for "two-bank chargers". Choose similar products for your boat with the number of banks that matches the number of batteries onboard your boat.

Outboard Motors - The water used to cool outboard motor drains out of the motor on its own when the boat is lifted out of the water, either on a lift or when put on a trailer and pulled out of the lake. As a precaution, the motor can be trimmed to the full up position (which it may already be if put on a trailer), then trimmed to the full down position when out of the water and stored in that position. The motor is designed to have the water drain out when trimmed to the full down position.

Antifreeze in Ballasts - Most wake boats have "ballasts" (tanks or bags) that are filled up to weigh the boat down and create a larger wake. These are usually emptied before trailering or lifting the boat at the end of the day. But at the end of the season, it's a good idea to check that they have been emptied all the way, and then add antifreeze to each one. This is as easy as pouring a gallon of pink RV/marine antifreeze into each ballast through the drain hose that exits the side of the boat hull, one for each ballast. Some companies charge as much as $200 for this service alone! Knowing what's involved and how to do it yourself can be a real money-saver.

Antifreeze in Heater - Some boats have heaters installed which use a heater core (similar to a small radiator) and hoses to route hot water exiting the engine through the heater core and a blower assembly to heat the cabin area of the boat during cooler times in the boat. These heater cores will freeze very easily in the winter and crack, so it's important to properly winterize them. That process is as simple as removing one of the hoses from the engine and spraying air through it until all of the water comes out (I use a 12v tube pump for that). Then, pour antifreeze into the line to fill up the heater core with antifreeze as an added precaution. See the winterization time-saver tips article to read how to make the heater hoses as quick and painless as possible.

Fogging the Cylinders - For a boat that will be stored for an extended period of time over the winter (months), it is a good idea to perform a fogging of the cylinders. This involves removing each spark plug and spraying fogging oil into each cylinder, and then turning the crank over by hand or "bumping" the engine over with the key when the safety switch is off, to coat the cylinder walls. In older boats with carburetors, this could be done by simply spraying fogging oil into the carburetor with the engine running without having to remove the spark plugs. But for fuel injected engines, spraying fogging oil into the intake manifold would foul the injectors so doing it through the spark plug holes is required. This step is a bit of a pain, which is why I have learned to drain my boat quickly on my own. That way I can simply drive the boat every month or so throughout the winter on warmer days, preventing the need to fog the cylinders.