How to Winterize a Pontoon Boat – Pontoon Winterization 101

how to winterize pontoon boat

Time flies when you are having fun. Sometimes it is hard to admit that winter is coming and that boating season is nearing its end.

And along with the temperature changes comes winterizing your pontoon.

For some, storing your pontoon boat can be an annoying thing to do, but for other pontoon owners, it is a fun ritual that is an integral part of owning a boat.

Of course, this is not as fun as spending a day on the lake, but it is necessary.

Cost to Winterize a Boat

Do you know how to winterize a pontoon boat?

If you don’t know how to winterize a boat, you might want to think about paying someone to do it for you.

How Much Does it Cost to Winterize Your Pontoon Boat?

It may cost you anywhere between $300 and $600. It depends on where you live and who is doing it for you, as well as what they are doing.

If, on the other hand, you would like to do it yourself, below are some tips for winterizing your boat. But, you should also consult your owners manual before you do that.

Boat Winterization Tips

Now that you have all the supplies that you need let’s create a winterizing checklist. Checklists can be tedious, but they exist for a reason, not to forget something. Skipping a critical step when winterizing your boat can be costly, so make sure you have the checklist to do it right the first time.

1. Remove Equipment

Remove everything of any value from the boat and store it in a safe place.

Removing equipment serves two purposes;

  • Protects your equipment from being damaged or stolen.
  • It makes the cleaning process more manageable.

2. Thoroughly Clean Your Boat

Once you have removed the equipment, thoroughly clean the entire boat as good as possible. It is much easier to clean the boat now than after the winter.

Also, pay attention to your carpet (if you have one). During the winter months, the air under the cover is a perfect place for mold and mildew to form. Proper cleaning is your best defense.

After you are done cleaning, polish the entire boat with a protective polish such as Meguiar’s.

MEGUIAR'S G13616EU Quik Interior Detailer Cleaner 473 ml
  • Safely cleans all interior surfaces with a matte finish
  • Contains sun blocking agents to preserve original appearance
  • Interior Detailer that will not leave behind a greasy appearance or feel

3. Winterize a Boat Motor

If you do not know how to winterize pontoon motor, ask someone who does.

Damage to your motor can be costly, so it is vital to pay close attention to winterizing it properly.

Because inboard and outboard engines are different, we are going to detail step by step process of proper winterizing for both of them.

How to Winterize Outboard Motor

How to Winterize Outboard Motor
Freshwater Flush

Make sure you pressure wash your engine to remove any dirt or salt. You can either use an extension for your garden hose or buy a pressure washer on Amazon, either works fine.

Drain Fuel Line and Carburetor

Disconnect the fuel line from the engine while the engine is still running. This will empty the fuel delivery component, and the engine will stop working. This is important to prevent any gums formation or clogging of lines inside the boat engine.

Fog The Carburetor Intake

Just before the engine stops working due to lack of fuel, spray fogging oil into the carburetor. This will help protect the internal surfaces of the engine cylinders and carburetors from corrosion.

When you see that the engine is starting to have a hard time running, that is the best time to add some extra fogging oil to make sure that every surface is covered thoroughly.

Drain cooling passages

Disconnect the battery from the engine.

With the motor in the upright position, remove the flush attachment and the engine from the flush tank. Let the water drain out.

Empty the powerhead and intermediate housing by opening and draining the plugs. You should probably consult your owner’s manual here.

Remove spark plugs and cover the inside with the fogging oil. It is helpful to rotate the flywheel a few times to help spread the oil inside cylinder walls.

This is not the wrong time to check your spark plugs, so you might want to consider doing that before you put them back in.

Don’t Forget To Lubricate

Consult your owner’s manual once more to make sure that all the surfaces needing lubrication and adequately covered with oil and heavy grease.

Drain And Refill Gear Case

Fill the oil tank back up to prevent condensation from forming inside the tank.

What To Do With Fuel Tank

You can either empty your fuel tank or fill the tank up to about 95% capacity.

I like to fill the tank for two reasons.

  • First, I don’t have to deal with draining the engine. I don’t find that particularly convenient.
  • Second, you want to fill the tank up to 95% to avoid and internal condensation inside the tank. This happens because gasoline contains ethanol and water may cause water phase separation.

What this means is that water will begin to remove the ethanol from the gasoline. It will, in turn, create a leaner combustion mixture between water and ethanol (higher air to fuel ratio). With more air comes stronger combustion and higher temperature, which can damage the engine.

It is vital to limit the space inside the talk to about 5% to limit the amount of condensation that can be created.

Also, make sure that you use a gas stabilizer to avoid the formation of passage-clogging gums.

Take Care Of The Propeller Shaft

If you are not taking the propeller home to prevent it from being stolen, make sure you clean it thoroughly and lubricate it well to prevent corrosion.

Store The Motor Upright During Winter

Lastly, make sure your motor is stored upright. By laying the engine to its side, you are risking leftover water draining to places where it should not go. You can quickly build something to allow you proper motor storage.

How to Winterize Inboard Engine

How to Winterize Inboard Engine
Change Engines Coolant

This only applies to freshwater engines. Over time anti-corrosion properties of coolant start fading away, so it is crucial to replace it annually to protect the inside of your inboard engine.

Change Engine And Transmission Oil

When changing the oil, it’s important to take the boat for a ride first. What this does is, it warms up the oil, which in turn separates contaminants off the engine walls, so when you drain the engine, you drain the pollutants as well.

And don’t forget to change the oil filter while you are at it.

Fuel Tank – Gas/Diesel

If you don’t want to drain the motor, fill it up the same way you would with the outboard engine for both gas and diesel engine. The reason is the same as for the outboard engine described above.

On the other hand, if you have a diesel engine, make sure to add some biocide to prevent bacteria growth.

Use a stabilizer for the gas engine.

If you have a diesel engine, you don’t have to use a fuel stabilizer unless you expect to run the engine during the winter. The reason why you don’t need the fuel stabilized is that once the weather gets warmer, the paraffin that precipitates out will be absorbed by the fuel.

Fuel Tank – Gas Engine

Empty the engine by shutting down the fuel supply and letting the engine run until it stops.

Fog The Carburetor Intake – Gas Engine

You can use the same steps to winterize an outboard boat engine as described above.

Flush Raw-Water Circuit

Use a freshwater flush connector if you have it.

If not, close the intake seacock. After that, on the outlet side of the raw-water pump, disconnect the hose. Also, disconnect the water cooling discharge hose from the manifold. Rinse it thoroughly with fresh water to remove any deposits and salt.

Drain Muffler Canister

In this case, less is better, less moisture that is. Try to minimize moisture in every way possible to reduce a chance of corrosion.

Grease Control Cables

Grease is your friend when working with the mechanical stuff, so use it.

Remove control cables from housing and grease them up.

If that is not an option, tape an oil-filled bag around the high end of the housing, let it sit there for a while so the oil can work its way down the cables.

Coat Unpainted Areas With Anti-Corrosion Spray

You should use anti-corrosion spray on all unpainted surfaces of the engine.

4. Winterize Your Battery

There are two options that you can do when you are preparing a pontoon battery for the winter.

If you decide to remove the battery from the pontoon boat, you will have to keep it indoors. It is essential to be stored in the place where temperatures don’t go below freezing. The garage or some extra space in the house would be an ideal place for keeping the battery safe.

On the other hand, if you decide to leave the battery onboard (which people usually do if they choose to leave the boat in the water), you will have to be careful and prepare your pontoon boat for these conditions.

Use a trickle charger to charge a battery fully before you store it. If you don’t have a trickle charger, you can take the battery to the marina or even an auto center for testing the battery, and charge if it’s necessary.

5. Take Care of The Gas Tank

Add fuel to your tank about three-quarters of the boat’s capacity. Someone would recommend more than that, but this is a perfect medium capacity for reducing condensation levels in the tank.

Add fuel stabilizer and switch of valves and seal exhaust ports. This step is significant because it helps in preventing inner corrosion to the tank.

6. Winterize and Store Your Pontoon

Get a quality pontoon boat cover and protect your boat before you place it into the storage. Nothing will protect your boat better, so make sure that you get the best pontoon boat cover you can.

Making proper steps in winterizing your boat is one of the most important things if you want to keep your pontoon boat safe and in shape for many years to come. Storing your pontoon boat should be a no brainer.

What Happens If You Don’t Winterize Your Boat

pontoon boat winterization

The worst thing that can happen to your boat if you do not winterize it is that water gets into small spaced and hidden areas. Once the water freezes, it will expand and, if the area can’t handle ice expansion, it will break.

The worst place for this to happen is probably the engine, but any damage due to uncovered boat is a bad thing, no matter how small the damage is.

So don’t play with this possibility, winterize your pontoon boat, get yourself the best boat cover and protect your investment.

I hope these tips for winterizing your pontoon boat were helpful to you and if you feel that I have missed something please let me know.

When Winterizing, Seal Everything

Try to seal all possible tank vents, air inlets, exhaust outlets and crankcase, and transmission breathers as best as possible. You have to prevent the moisture of getting inside your engine as best as you can.

Get a quality pontoon boat cover and protect your boat before you place it into the storage. Nothing will protect your boat better, so make sure that you get the best pontoon boat cover you can.

I would also recommend you do this on a dry day, even the moisture in the air could be enough to cause issues over the long winter months.

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  • Genuine OEM Yamaha Part
  • Lubricates And Protects Internal Engine Components
  • Vital For Proper Winterization And During Extended Storage Periods


This is a very important process in boat maintenance prior to storing your boat for winter. So do not overlook these winterization steps and read the article multiple times if you have to. Take notes or print it out and take it with you when you decide to winterize your boat.

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