How to Winterize a Boat: An Expert Guide

Maintaining your boat is the best way to keep making great memories on it for as long as possible. Regular maintenance is already part of your routine, but boats require special attention at certain times of year — like when being stored for the winter. 

When you’re done enjoying the water for the season, follow our detailed guide on how to winterize a boat.

Why Winterize a Boat?

Effective winterization today prevents costly repairs tomorrow and ensures a smoother start to your next boating season.

When thinking about winterization, many focus primarily on their engines — but proper winterizing protects far more than just the engine. The winterization process safeguards your entire boat, inside and out, with benefits like:

• Protecting the engine: If you don’t winterize your boat, water could freeze inside the engine, cracking it entirely or creating other internal problems.
• Stabilizing fuel: You can keep fuel fresh and unfrozen by using a fuel stabilizer to keep condensation from accumulating.
• Maintaining battery life: Properly removing and storing batteries prevents damage and power drainage.
• Safeguarding the hull: Winter is harsh on paint and boat materials, but you can prevent blistering and other issues by winterizing.
• Preventing mold and corrosion: A boat that’s clean and dry both inside and out is less likely to develop mold and moisture-related corrosion.
• Ensuring lubrication: Lubricating protects against rust and corrosion of moving parts.
• Deterring pests: Rodents and insects can make a big mess during the off season, but winterizing keeps these pests out.
• Preserving the interior: Thoroughly cleaning your boat’s interior and removing sensitive items ensures it stays safe all winter long.

Tools for Winterizing Your Boat

To winterize your boat successfully, you’ll need:

• An air compressor for clearing water lines
• Non-toxic antifreeze to prevent freezing in systems
• Fuel stabilizer to keep fuel from deteriorating
• An automatic battery charger to preserve battery charge
• Basic tools for water draining and simple repairs
• Marine-grade lubricants to protect moving parts
• Eco-friendly supplies for a thorough cleaning
• High-quality covers for your boat and equipment

How to Winterize a Boat: Step by Step

Don’t be intimidated by the length of your boat winterizing checklist; taking it step by step makes it simple. Here are the key parts to focus on and our best tips for how to winterize a boat the right way:

1. Engine and Cooling System

Start by draining any water from the engine. This will prevent freezing and cracking. Next, fill the system with antifreeze designed for marine engines. We recommend a non-toxic, propylene glycol-based antifreeze, which is safe for the environment and your engine.

2. Fuel System

Fill your fuel tank to reduce space for condensation. Otherwise, your fuel tank could freeze and become damaged. Adding a fuel stabilizer will prevent the fuel from degrading. Be sure to use a marine-specific fuel stabilizer, then briefly run the engine to distribute it through the system.

3. Battery

To prevent cold damage and discharge, disconnect and remove your fully charged battery, and then store it in a cool, dry place. A battery maintainer isn’t strictly necessary, but it can help your battery stay charged and in top condition during long winter months.

4. Bilge and Pumps

Clean your bilge and pumps thoroughly, ensuring all water is removed from the system. You can also add antifreeze to prevent any residual water from freezing and causing damage. While you’re cleaning, you have a great opportunity to check for and repair any leaks before they worsen over the winter.

5. Freshwater System

Drain all tanks, water heaters, and lines, then pump non-toxic antifreeze into the system. When you’re ready to get back on your boat again, first flush the system with fresh water to make sure it’s clean and safe.

6. Interior

To guard against theft, remove all valuables and electronics before you store your boat. And don’t forget to double-check for perishables (unless you look forward to the smell of rotting food next year).

Clean the interior of your boat thoroughly and leave compartments slightly open to ensure air circulation and prevent mold and mildew. We suggest using moisture-absorbing products and mildew inhibitors to protect interior surfaces.

7. Exterior and Hull

Weather and UV rays both pose risks to the exterior and hull of your boat. To safeguard against both, start with a deep clean and then apply a coat of protective wax. Finally, cover the boat with a well-fitted, breathable cover. Ensuring a great fit helps prevent pooling water and ice formation, which can stress the boat structure.

8. Drives and Lower Units

Now is the time to check for and repair any damage to your drives and lower units. Pay close attention to seals and gaskets — leaks could let water in and cause ice damage. To prevent other moisture-related issues, change the gear oil.

9. Steering and Control Systems

You can stop corrosion in its tracks and ensure smooth operation in the spring by lubricating moving parts in your steering and control systems during winterization. Using marine-grade lubricants and protectants designed for your system will maximize effectiveness.

Remember to always refer to the manufacturer’s guidelines or consult a professional as you winterize to make sure you’re protecting your boat the best you possibly can.

How to Winterize a Boat: Special Considerations

Winterizing looks a little different for every type of boat and storage strategy. Tailor your approach to your specific boat and scenario for effective winterization.

Engine Types

You’ll follow a slightly different process for winterizing each engine configuration. But when it comes down to it, an engine is an engine, whether it’s on a sailboat or a motorboat.

Here’s a simplified overview of a few different tasks you may encounter:

• Sailboats: Protect sailboat engines from freeze damage by draining the engine and tank, then adding antifreeze.
• Inboard engines: In addition to draining water, you’ll need to flush the cooling system, fill up the fuel tank, use fuel stabilizer, and protect internal components from corrosion.
• Outboard engines: You can remove an outboard engine and store it separately, but you may still need to drain, lubricate, and apply antifreeze to certain components.
• Inboard-outboard (sterndrive) engines: Blend the inboard and outboard approaches to motor maintenance, focusing on draining, fuel stabilization, and changing the oil.

Storage Scenarios

Let’s go over the last few items on your winterization to-do list, depending on where you store your boat.

For boats stored in water:

• Close all seacocks to prevent water entry, except in the cockpit, where you still want to let water out.
• Tighten rudder shafts and stuffing boxes to prevent leaks.
• Inspect dock lines to make sure they’re durable enough to stand up to winter conditions.

For all boats:

• Clean and dry all storage areas to stop mold and mildew from developing.
• Leave the marine refrigerator open to avoid odors and mildew.
• Store cushions vertically to enhance air circulation and prevent mildew.
• Use moisture absorbers throughout the boat to further lower the risk of mold and mildew.

Want to learn more about boat maintenance, safety, or navigation? Our captain’s license courses prepare you for every season! Learn more about studying with us today.