How To Winterize a Boat

Boat covered in snow

The winter season is wonderful. What’s probably not so wonderful though, is the potential damage it can do to the boat that helped you seize the remaining days of sea and sunshine.

Unless you live in the sunny South or Hawaii, you should really winterize your boat before the temperatures drop below freezing point. Winter can get harsh so a bit of upkeep can keep your boat safe. Otherwise, any residual water droplets may freeze, expand, and ruin your boat’s inner components like the engine and hose.

It’s not difficult to learn how to winterize a boat. However, if you skip a process as simple as removing a drain valve, you might end up with thousands of dollars in repair costs to replace the engine. And there is no guarantee that your boat insurance will cover such cost.

But with the right approach and planning, you’ll get it done in no time. And if you’re not sure where to begin, I’ll walk you through the process of winterizing your boat with a few simple steps.

How To Winterize a Boat: Follow These 10 Easy Steps

Winterizing your inboard, outboard, or stern drive engine boats can help you save money on repair costs. Keep in mind that each boat has its distinct set of features and elements, so it’s always best to refer to your handbook for specs.

Here are ten easy steps to help keep your boat safe during the cold winter.

Step 1: Prepare and get your tools

Hiring a professional to winterize your boat can cost you money. So, paying the upfront cost for the tools and materials (which I’ll go over later) can be a great investment and will be cost-effective in the long run.

Consider making a checklist of things that need fixing, replacement, or adjustments. This could be the old electronic parts, foul-smelling holding tank, carpets, or maybe the stuck winch. After you’ve noted all the things that you need to fix or change, plan your project to make sure it’s ready for springtime.

Step 2: Replace the engine oil

Since moisture and acids in old oil may damage bearings and other engine components when stored, you need to drain it. You can do so by warming up the engine while submerged in water to allow more oil to drain and contaminants to wash out.

Another way you can do this is by pulling out the dipstick and inserting a suction hose into the tube to drain all of the old oil. You can buy oil pumps from your local auto parts store.

If your boat has a 4-stroke outboard motor, you must replace the oil and the filter. Make sure to follow the boat manufacturer’s recommendations on oils and filters.

Step 3: Drain the coolant

You must drain water off your engine to avoid harm due to expanding frozen water. This is a very important step as any droplet of water can ruin your boat’s components.

If your boat has an inboard or sterndrive engine, you must clean the engine with water by connecting a hose to the cooling system using water muffs. After that, cleanse the engine until it returns to its normal working temperature.

Then, take off the drain plugs, which are often found in the engine compartment and manifold. Disconnect the water pump pipe if necessary to drain any residual water.

If your boat has an outboard engine, check that all drain outlets are clear. Next, turn on the engine and flush the cooling system with clean water for a few minutes. Again, you can connect a garden hose to water muffs to accomplish this task.

While some boat owners prefer to keep the engine block flushed but emptied for the winter, other boat engine manufacturers advise that the whole engine be filled with non-toxic antifreeze. You must always follow the instructions provided by the manufacturer of your engine.

Step 4: Stabilize your fuel

Adding a fuel stabilizer to the tank helps avoid fuel deterioration. Fuel can degrade quickly which can cause gunk and varnish to accumulate in your engine, which can affect its performance in the future.

It’s worth noting that burning up all your fuel won’t keep varnishes from building up in the engine. This is due to the fact that there will always be residual fuel. Plus, gaskets might dry up and draw leakage in the spring.

You should also make sure that you’re refilling the tank with fresh fuel to avoid highly corrosive water condensation, which can form in an empty or low-fuel tank. And while you’re at it, replace your fuel filters and water separators to get everything set for the coming year.

Step 5: Protect the internal components of the engine

Engine oil leaks out when you store it. This exposes the internal engine components to harsh conditions in the winter. And in the springtime, this can result in corrosion and metal-to-metal friction, known as cylinder scuffing.

You can avoid such problems by applying a fogging oil spray. It’s a solution specifically formulated to permeate deep into the engine. This formula also treats the internal components with an anti-corrosive coating.

Step 6: Change the gear oil

It’s advisable to replace your gear oil before the winter because if water gets into the chamber, it can freeze and cause significant damage to the internal parts. This can sometimes end in a broken casing.

To do this, you need to drain the old gear oil from the bottom unit and put in a new supply. In replacing the gear oil, inspect for any moisture. You might see water flowing out first or observe milky or lumpy oil. This indicates that your boat has moisture contamination and will require new sealing.

Step 7: Lubricate

Look for the grease fittings on your engine, which can be found in the steering gear section. Then, apply a high-quality marine lubricant to safeguard it against rust, oxidation, and corrosion.

One of the best ways to lubricate the engine is to insert the pump nozzle and inject the fresh lube until it exits the upper vent. Then, put replacement gaskets in the drain and vent openings and plugs. Next is removing the bottom drain valve on the lower unit, and allowing the lube to drain before detaching the top vent plug.

Once you’ve drained the old lubricant, you can now replace it with fresh lube. You may refer to the user manual to ensure you haven’t overlooked any vital spots that require lubrication.

Step 8: Unpack your boat

In the winter, boatyards have less activity, making any type of robbery easier. Make sure to take out all valuables such as electronics, life jackets, and fire extinguishers. It’s also a good idea to empty your icebox if you have any.

Remember to also remove and wash your linens and blankets and allow the pillows and cushions to air out.

Step 9: Pressure wash the exterior

The exterior of your boat needs a thorough cleaning before storing it for the winter. Pressure washing your boat is an efficient approach to removing filth and algae growth. As well as other debris from the outside surface.

Before covering your vessel, make sure you pressure wash the hull, propellers, shafts, and rudders to get rid of dirt or any residue from saltwater.

Step 10: Cover your boat

Dry storage is the safest option for your boat, though it may be costly—particularly in locations with harsh and long winters. At the very least, you’ll need to protect your boat with a sturdy covering. Shrink wrapping your boat is another viable solution. And finally, choose your preferred location, service, and way to store your boat.

Required Materials for Winterizing Your Boat

Getting all of your materials available in advance will save you stress from taking a last-minute trip to the hardware store. Below is a list of the things you’ll need:

  • Gaskets for drain plugs
  • Engine oil
  • Filters
  • RV antifreeze
  • Fogging oil
  • Fuel stabilizer

Required Tools for Winterizing Your Boat

Before you begin your project, make sure you have all of the tools you’ll need for the boat winterization. Having them ready saves you time and stress.

  • Nut driver
  • Water muffs
  • Socket and ratcheting set
  • 4-in-1 screwdriver
  • Set of wrenches
  • Oil suction pump
  • Lower-unit injection pump

Tips for Boat Storage

When you’ve finished winterizing your boat, you need to think about how you’ll store it. But before you do, you need to consider a few things. Laying a durable cover over your boat will keep the snow out, but there are also other great ways for doing so.

Some boat owners adopt wood frames and tarps, while others build polyvinyl chloride (PVC) castles with lovely canvas coverings. Many boat owners also shrink-wrap their boats. Every approach has upsides and downsides, but it really boils down to your personal choice.

Make sure to your owner’s manual for any extra instructions or winterization practices. If you’ve not done this one before, you may contact someone with the skills and experience or consider hiring an expert.

Things You Must Do When Storing Your Winterized Boat:

  • Store your boat with the stern down so that rain and snowmelt may escape through the bilges.
  • For minimizing frost damage, keep all seacocks and drains open.
  • Add fuel stabilizers and winterize engines and components according to the manufacturer’s instructions.
  • Boat coverings and tarps should never be tied to boat supports.
  • Trailer boat hulls must be supported so that the weight does not fall entirely on the tires.
  • Install moisture-absorbing elements in the storage.
  • Take out food, electronics, and valuables and keep them at home during the storage period.
  • Don’t use a portable heater or an auto battery charger in the boat’s blige.
  • Inspect stands and blocks on a regular basis throughout storage if the boat is obstructed.


Do you leave antifreeze in the boat engine?

You may leave it outside for the winter, just make sure to reassemble it in the springtime with a fresh gasket.

How do I winterize my boat with antifreeze?

To winterize your boat with antifreeze, you must first loosen the raw water intake hose from the seacock. Note that doing this can be a challenge at times since hose fittings and hoses can get mechanically frozen onto the spot.

After removing the intake hose, place the tip into the antifreeze in the container. Then, turn on the engine and keep it at idle for 30 seconds or longer until antifreeze runs out of the exhaust outlet.

Do outboards self-drain?

A self-draining cooling system is included on all outboards of boats. So, there really is no point in starting the engine with the intention of removing the remaining drips from the water pump chamber.

What happens if you don’t winterize your boat?

If you don’t winterize your boat, water freezes and expands. And this can damage whatever is stuck inside. When this happens, water may infiltrate through unprotected places. This can result in a damaged engine caused by acidic and corrosive wastes, as well as salt and rust accumulation.

When should I winterize my boat?

Most people do not base their decisions on a certain day. Instead, the ideal time to winterize a boat is after the boating season has ended. It’s the time when you will no longer be using your boat for the rest of the year.

Should I drain antifreeze after winterizing the boat?

Since air doesn’t freeze, it’s best to leave the system emptied. Marine engine antifreeze, however, includes water and it encourages corrosion.

Final Thoughts

The thought of winterizing a boat might send shivers down your spine. Particularly the timeframe that usually indicates the end of a blissful boating season. Also, winterizing your boat may be way down the list of interesting things to do during the winter.

But, come on now, boat ownership can’t be all fun and cool. To safeguard your boat, keep it at top performance, and the engine healthy, you must do a list of maintenance jobs.

I hope you’ve found this helpful in winterizing your boat. Make sure to plan it ahead and adopt all of the steps and tips I’ve shared so your boat can survive. I can’t wait for you to enjoy the boating season again.

Good luck!

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