Best Way To Winterize A Boat – According to Experts!

Winter in some regions can be pretty brutal, and if you don’t winterize your boat, the engine and other parts can freeze, leading to damage that may require expensive repairs. And, of course, you want to avoid this at all costs. Right? There are countless articles and tutorials online, which can be confusing. But no worries, this article has you covered. Here, you’ll find the best way to winterize a boat to keep it in good condition for a long time.

Take Away

The best way to winterize a vessel is to use it all year round. However, if you plan to store it for a long period, you should follow the following steps: Draining the engine of water, adding a fuel stabilizer, changing the oil and filter, greasing fittings, and protecting the boat with a cover. It is also important that you follow the manufacturer’s winterization guidelines and consult with boat winterization services if needed.

When Is The Right Time To Winterize Your Boat?

Well, it depends on where you live and the type of boat you have. Generally, if you live in a climate that has cold winters, you should consider winterizing your boat in the Autumn, around October or November at the latest, to avoid freeze damage. In other words, at the end of the season. However, you should winterize your boat even if you plan to lay it up for several weeks to prevent costly damage when you return to the water in spring.

6 Simple Steps to Winterize Your Boat

1 – Prepare Your Boat

You want to clean the boat exterior, including the hull, before storing it away for the season. Waxing your boat will protect the surface over the winter. Doing it at the end of the season also makes the preparation much smoother and quicker in the spring. Also, it would be a good idea to clean the interior to prevent any moisture and mildew build-up.

Clean the boat exterior.

First and foremost, give your boat a thorough cleaning. Wash the exterior with a mild detergent and water, scrubbing away dirt or grime. Pay special attention to areas that may be prone to mold or mildew. 

Next, apply a coat of marine-grade wax to your boat’s hull to protect it during storage.

Clean boat interior

Remove all gear and equipment and store them indoors. This includes life jackets, electronics, cushions, and any valuables. If you don’t bring them home, ensure all those items are completely dry before storing them in the boat. Vacuum and clean the upholstery, carpet, and floors. Ensure to wipe down surfaces, like countertops and tables, with a mild cleaner. This process will help keep your boat fresh and free from mold and mildew.

2 – Winterizing the Freshwater System

It’s crucial to use a proper, non-toxic antifreeze, such as propylene glycol, to protect your boat’s freshwater system from freezing. Here, l walk you through the steps to winterize your boat’s freshwater system efficiently and effectively.

  • First, empty out your freshwater tanks by opening all the faucets and turning on the freshwater pump. Let the faucets run until the tank is dry, then close them and turn off the pump. Draining the system prevents any leftover water from freezing inside the pipes and causing damage.
  • Next, fill your freshwater tanks with non-toxic antifreeze. Opt for a propylene glycol-based product, as it is safe for the environment. Never use ethylene glycol because it’s toxic. Pour 6 to 8 gallons of antifreeze into the tank, preferably with a rating of at least -50 degrees Fahrenheit. If your boat is stored where the temperature falls below -0 degrees, then you will need to use an antifreeze with a -100 degree rating. If your boat has a water heater, add some extra gallons of propylene glycol antifreeze.
  • Once you’ve added the antifreeze to your freshwater tanks, open all the faucets again and turn on the pump to circulate the antifreeze throughout the system. Make sure to run enough antifreeze through each faucet until you see the colored antifreeze flowing out, indicating that your pipes are protected. Make sure not to forget any showers, heads, and freshwater washdown spigots.
  • Finally, close all the faucets and turn off the pump. Your boat’s freshwater system should now be protected from freezing temperatures during the winter months. 

3 – Winterizing the Fuel System

One of the most important aspects of fuel system winterization is adding a fuel stabilizer to your boat’s fuel tank. Fuel stabilizers, like Techron Marine, help prevent the formation of gum and varnish residues that can clog the fuel system. Additionally, it helps maintain the quality of your fuel throughout the winter months. 

  • First, you will want to add the recommended amount of fuel stabilizer to your fuel tank, following the instructions on the product label.
  • Next, you should fill up your fuel tank with fresh, quality fuel. A full tank reduces the likelihood of condensation forming inside the tank during temperature fluctuations over the winter season. Condensation can lead to water mixing with the fuel, increasing the risk of phase separation and potential engine damage.
  • After adding the fuel stabilizer, run your engine for a few minutes, allowing the treated fuel to circulate through the entire fuel system. This step ensures that the stabilizer reaches all parts of the system, including the fuel lines, carburetors, and fuel rails or injectors. Running the engine also helps to remove any old, untreated fuel remaining in the system.
  • Inspect the fuel hoses for any signs of wear, such as cracks or soft spots. Damaged hoses can lead to fuel leaks and should be replaced before storing your boat for the winter.
  • A crucial component of the fuel system is the fuel-water separator. Change the fuel filter and drain any visible water from the separator, preventing any moisture from reaching your engine. Moisture in the fuel system can cause poor performance, corrosion, and other costly issues.

4 – Winterizing the Bilges

If your boat stays in the water for the off-season, winterizing your bilge pumps won’t be necessary unless you want to. But you’ll have to make sure they all work properly. Now, if you keep your boat on land, here are the steps you need to follow:

  • Begin by draining the water from the bilges and other areas, such as raw water washdowns, live well pumps, and bilge pumps. The easiest way to do this is to open your boat’s through-hull fittings and let the water flow outsource.
  • Once you’ve drained the water, you can then add some antifreeze to the bilge area as well. Pouring in a small amount of marine, non-toxic antifreeze will help ensure that any remaining water doesn’t freeze and potentially damage your boat’s bilge areas.

5- Winterizing An Inboard Engine

The steps vary depending on the type of engine and boat, so always consult your owner’s manual for specific instructions. However, here are general steps to winterize an inboard boat engine:


  1. Read the Owner’s Manual: Review the owner’s manual for your boat and engine to understand any specific winterization requirements or recommendations from the manufacturer.
  2. Change the oil: Warm up the engine by running it for a few minutes to help the oil flow more easily. Place an oil drain container underneath the oil drain plug. Get the oil drain plug out and allow the old oil to flow into the pan. Remove and replace the oil filter. Add new oil according to the specifications in your owner’s manual.
  3. Flush the Cooling System: Attach hose muffs to the water intake ports on the bottom of the boat. Turn on the water supply and start the engine. Let the engine run for a few minutes to flush out any saltwater or debris from the cooling system. Once done, turn the engine off.
  4. Fog the engine: With the motor running, spray fogging oil directly into the air intake of the carburetor or throttle body. This will protect internal engine components from corrosion. Shut off the engine while continuing to spray fogging oil until it stalls.
  5. Change the Fuel Filter: Replace the fuel filter to ensure no contaminants are present in the fuel system. Pour a fuel stabilizer into the gas tank according to the manufacturer’s instructions.
  6. Drain the Water System: Open drain plugs and valves in the engine block, exhaust manifolds, and any other water-cooled components to allow any remaining water to drain out. Close the drains after the water has drained out.
  7. Fill with antifreeze: Disconnect the hose from the muffs used for flushing. Pour marine antifreeze (propylene glycol-based) into a bucket. Start the engine and use a water pump to draw antifreeze from the bucket into the cooling system. Continue until pink antifreeze flows out of the exhaust.
  8. Inspect and Lubricate: Inspect all belts, hoses, and clamps. If you see any signs of wear or damage, replace them. Lubricate any moving parts, such as throttle and shift cables, with a marine-grade lubricant.
  9. Disconnect Batteries: Disconnect the boat’s batteries. Clean the terminals with a layer of dielectric grease to protect them. Store your batteries in a cool, dry place and connect them to a battery tender.

6 – Winterizing An Outboard Engine.

A 2-stroke outboard motor does not require the same winterization procedures as a 4-stroke motor on a boat. Each type of engine has its own specific requirements for winterization due to differences in their internal workings and lubrication systems.

Here are some key differences in winterization procedures between 2-stroke and 4-stroke outboard motors:

  1. Fuel Stabilization (both): Both 2-stroke and 4-stroke engines benefit from adding a fuel stabilizer to the fuel tank before storing the boat for the winter. A stabilizer helps prevent the fuel from deteriorating and clogging the fuel system.
  2. Oil Mix (2-Stroke): In a 2-stroke engine, you need to ensure that the oil-fuel mixture in the tank is properly mixed and that the oil injection system (if equipped) is functioning correctly. You may also need to fog the engine by spraying fogging oil into the carburetor or spark plug holes to protect internal components.
  3. Engine Oil (4-Stroke): For a 4-stroke engine, you should change the engine oil as well as the oil filter before winterizing. This helps remove any contaminants and ensures fresh oil is in the engine during storage.
  4. Flushing the Cooling System(Both): For both types of engines, you must flush the cooling system using fresh water with the engine tilted down to allow the water to drain completely. If your outboard has a flushing port, connect the hose and flush, and there is no need to run the motor afterward. Conversely, If you use earmuffs, you must run the engine after the flushing procedure. However, always follow the boat manufacturer’s recommendations.
  5. Battery Maintenance (Both): Regardless of engine type, you should remove the boat’s battery and store it in a cool, dry place. Connect it to a battery tender to keep it charged when not in use.
  6. Corrosion Prevention (Both): Apply corrosion protection to metal surfaces and electrical connections to prevent rust and damage during the winter.
  7. Spark Plug Removal (Optional): Some boat owners prefer to remove spark plugs and spray a small amount of oil into the cylinders to protect against rust.
  8. Propeller and Lower Unit (Both): Grease the propeller shaft and the lower unit’s fittings to prevent corrosion and ensure smooth operation when you use the boat again.
  9. Cover and Storage (Both): Cover your boat with a properly fitted boat cover.

Frequently Asked Questions

Q: How can I properly fog a boat motor?

To properly fog a boat motor, you should warm up the engine first. Then, apply a fogging oil spray into the air intake or carburetor while the engine is running. Continue spraying until you notice thick smoke coming out of the exhaust.

Q: Can I winterize a sterndrive boat on my own?

Yes, you can winterize a sterndrive boat on your own if you follow proper guidelines and have some mechanical knowledge. You’ll need to perform tasks like changing the engine oil, lubricating moving parts, draining water from the engine, and pouring antifreeze into the cooling system. If you have no skills or feel uncomfortable with the process, it’s best to get help from a specialist.

Q: Should I empty the fuel tank during boat winterization?

Boat winterization specialists recommended draining the old fuel and refilling the tank with fresh fuel at least three-quarters full. Then, treat the fresh fuel with marine grade fuel stabilizer additive to prevent condensation and degradation of the fuel. This helps maintain your fuel quality for the next boating season. It’s important to go for a short ride on the water or run the motor for several minutes after adding the fuel stabilizer to effectively distribute the fuel.

Q: Are there boat winterization kits and services available nearby?

Many marine supply stores and boat repair services offer boat winterization kits or professional winterization services. You can check out local boat dealers or marinas to find these resources. Additionally, some businesses might provide mobile services that come to your location to assist with the winterization process. To find options near you, try searching online or ask fellow boat owners in your area for recommendations.

Final Words

As you can see, winterizing a boat requires a little work, but it’s really worth it, as this will keep your boat in good condition while not in use and save you costly repair, time, and nerves. However, if you don’t want to bother with the winterization or need help, you can have a professional do the tasks. 

Want More Tips?

Subscribe to Cruising Sea newsletter to receive every two weeks the latest posts straight to your inbox!

4 thoughts on “Best Way To Winterize A Boat – According to Experts!”

  1. What a thorough and comprehensive guide. Thank you Daniella.

    I am nowhere near an expert myself, but it is very eye-opening to learn how much really goes into maintaining boats to keep them in good condition. In fact, the term “winterizing” is completely new to me.

    I commend you on the proactive approach you took by including FAQs. Great article.

    • Hi Yusuf,

      Absolutely, I’m glad you found the guide helpful! Maintaining boats can indeed be a complex task, and the term “winterizing” refers to preparing a boat for the winter season to prevent damage from the cold weather. It’s great to hear that you found the FAQs helpful, too; they can really provide valuable insights and answers to common questions. If you have any more questions or need further information, feel free to ask. 
      Thank you for the comment, and I wish you a wonderful day!

      Happy boating!

  2. Winterizing a boat is crucial to keep it in good condition, especially in regions with harsh winters. The comprehensive steps and explanations you’ve provided in this article are incredibly helpful for boat owners. It’s evident that proper winterization can save a lot of hassle and potential damage.

    I’d like to ask, for someone new to boat ownership, what are the essential tools and supplies they should have on hand when preparing to winterize their boat?

    Relevant insights!

    • Hi Claude,

      When it comes to winterizing your boat, having the right tools and supplies on hand is essential to make the process smooth and effective, especially if you’re new to boat ownership. To answer your question, you can use all the tools mentioned at the beginning of the article. 🙂 

      I hope it helped, and if you have more questions, don’t hesitate to ask. I’ll be more than happy to assist.

      Thank you for the comment, and I wish you a great day.


Leave a Comment