Show Your Boat Some Love By Winterizing It Right

How To Winterize Your Boat

It’s the end of another fun boating season. Now the work starts. But it’s necessary if you want to be on the water next year. Does the question then become how to winterize boats? Fortunately, with a little prep, you can get the job done and save yourself some cash too.

Why You Should Winterize Your Boat

Winterizing isn’t difficult, but it is a messy job. It’s best done on land so that you can also take the time to inspect the rest of the engine and hull. It’s essential because any water or moisture still instead of the boat can damage parts or crack the engine block. Perhaps the neglect of this seasonal task led to the acronym, “Break-Out-Another-Thousand” to represent an expensive spring repair.

It’s also an excellent opportunity to get the boat ready for next year. It’s imperative for inboard and stern drive engines. The steps are similar with slight differences between stern drives, inboard, and outboard engines.

Even if you live in a warmer climate, it’s still wise to invest the time in it. It doesn’t take long for freezing temperatures to damage your boat, leaving you with a hefty freeze-related insurance claim.

What You Will Need

You must have the following equipment to winterize your boat correctly:

  • Garden hose
  • Antifreeze
  • Earmuffs for flushing the motor
  • Fogging oil
  • Fuel stabilizer
  • Wrench
  • Winterizing kit or 5-gallon bucket
  • Oil filter, pump, and oil

You should consult your craft’s user manual for the manufacturer’s recommendations on the types of products you should use. Otherwise, you might find yourself looking up a boat payment calculator.

How to Winterize Boats

The process includes several steps to protect the interior, exterior, and engine of your boat. While you can do them in any order, it makes sense to begin with the last one since it can cause the most mess. There are slight variations, depending on the vessel. The narrative will focus on a stern drive. It differs from an inboard with a steerable lower unit is while the former uses a rudder to navigate.

Start With the Engine

There are four steps to get your boat ready for winter. It’s essential to follow them in order. First, top off the gasoline. There are two schools of thought on this step. Some think that it’s wise to top off the tank to prevent condensation which could damage it. Adding fuel stabilizer helps prevent it and preserve the quality of the fuel. It’s also a good time to replace your fuel filter and fuel-water separator.

Add Coolant

Next, it’s time to winterize the engine block to keep it from cracking. Attach your garden hose to the earmuffs and place them over the raw water intake. Then, run the water and start the motor. The purpose is to warm the engine so that the thermostat will open. It will also ensure that the antifreeze circulates throughout the system.

You’ll need to use the earmuffs with other types of engines too. It can cause significant damage if they run dry, putting you in the market for used outboard motors.

Add antifreeze to the winterizing kit. It will take about 4-5 gallons. Attach it to the earmuffs and turn on the engine. The coolant will circulate through the engine until the container is empty. You’ll notice it discharging. Turn it off again. Marine or RV antifreeze differs from the type you’ll use in your car because it is non-toxic.

With an inboard engine, you will remove the raw water intake and place it in a 5-gallon bucket filled with coolant. Then, continue following the procedure. It’s a smart idea to inspect the impeller at this time. If it fails when you’re on the water, your boat will overheat. You don’t need to do this task with an outboard or personal watercraft.

Fog the Engine

This step will protect the system from corrosion that can occur when the moisture in the air condenses. Remove the flame arrestor on the carburetor and spray it thoroughly inside the unit. Your engine may stall or sputter at this point, which is all right. Turn off the motor. You can also coat each of the spark plugs.

Do an Oil Change

This step ensures that the residual acids from the combustion of the engine won’t wreak havoc with your engine while it sits for an extended period. You will need an oil pump, filter, and the correct 4-stroke oil for your engine. The first item is necessary since the drain hole is hard to get to under the craft. It also makes the job less messy. Make sure to dispose of the used fluid and filter properly.

Check the Lower Unit

It’s also necessary to drain and replace the lower unit fluid. Remove the vent and drain plugs to allow the fluid to flow out of it using a pump. Once it’s done, replace them. Look it over, paying close attention to the prop. You can remove it and have it repaired if it has dings.

Interior Check and Prep

You will also need to service the fresh and wastewater systems of your boat if you have them. The process is similar. You will begin by opening all the faucets to remove the water. Then, follow up with antifreeze and pump it until the discharge runs pink. For the latter, make sure that you pump the holding tank first.


Mildew and mold are your boat’s worst enemies. Perhaps nothing will have you researching new boat prices faster than a stinky craft. Open all doors to allow air to flow. Remove any valuables like fish finders or GPS units from the cabin. Ideally, you can store the cushions off-site. If not, set them upright so that they can stay dry.

Pump out any remaining water in the bilge. Don’t let it flow to the ground. Sometimes, it contains oil or other contaminants. Add antifreeze to protect the pump. Take out the battery and keep it on a trickle charge. Store it on wood instead of concrete. Putting it on the latter will cause it to discharge and corrode. You should place one or more desiccants inside to absorb any moisture and prevent mold.


Keeping your boat on the trailer or jack stacks will help it dry out completely and protect the finish on the fiberglass. Remember to remove the drain plug and put it in a safe place. Look over the trailer and check the tires. Put the cover and a tarp over it. Your boat is now ready for its long winter’s nap.