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How to Winterize a Boat

How to Winterize a Boat

Wondering How To Winterize a Boat? Sea and sunshine fill the summer in the midst of enjoying our motorized boats on the water. But, as the cooler months approach, we have to winterize the boat.

Whether your boat has a gas inboard, outboard or stern drive engine, winterizing will be imperative. There are several things you have to do to ensure your boat will be in tiptop shape the following year.

Winterizing a Boat

The biggest issue with winter boat storage is water. Freezing water expands which can damage pipes and lines. Plus, it promotes corrosion along with mildew and mold growth. Follow the steps below to prevent frozen water damage:

1. Prep the Engine

Warm up the engine first to help the dirty oil loosen up. Doing this will also make other impurities flush out easier. But, this will depend on the kind of engine you have.

  • Stern Drive ; Inboard Engines: Flush with clean water using water muffs or a similar device. Water muffs allow you to connect a garden hose to the cooling system. Run it until the engine obtains a normal temperature.
  • Outboard Engines: Ensure all drain holes are open and then start the engine and flush with fresh cool water. Once again, you should use something like water muffs.

2. Drain All Water Systems

You have to remove all water from the boat. This means you have to check all tanks, sinks and heads along with raw water, wash downs, live wells and bilge pumps.

3. Remove Drain Plugs

Once all the water is out, you have to remove the drain plugs. Often found in the engine block and manifold, you might have to take out the water pump hose so all remaining water drains out.

4. Protect the Boat’s Engine from Corrosion

Once you’ve flushed the engine, you have to protect it from corrosion. Unfortunately, the boat will drain oil while it sits in storage. This exposes the engine and its components to winter weather which leads to corrosion and cylinder scuffing in spring.

Replace engine and gear oil with fresh, high-quality oil. Your owner’s manual will have suggestions for what kind you should get. Also, get a fogging oil spray. This will penetrate into the engine and coat everything with a protective layer.

5. Add Fuel-Stabilizing Additive

Because fuel can deteriorate in as little as two months, it can cause varnish and gum to buildup in the engine. This will make it difficult to start along with a reduced lifespan and poor performance. Draining it won’t prevent these problems either; causing additional issues like drying out the gaskets.

Add a premium fuel stabilizer designed for marine use. Fill the tank with fresh fuel to prevent water condensation and add the stabilizing agent. Run the engine for a few minutes to get the treated gas throughout the system.

6. Cleaning ; Storage

Ensure the boat’s outside is clean and waxed. Then cover your boat and put it in dry storage. This can be a space you rent, a garage or covered structure in your yard. Some people even shrink wrap their boat for the winter, especially if they live in a climate with a long winter and have to keep the boat outside.


The most important aspect to winterizing your boat is to make sure you drain out as much water as possible. Water is the number one cause of engine, pipe and line failures when the boat starts up again in the following spring. It can be costly to replace and repair. Plus, it inhibits enjoyment of the sun and sea in summertime.


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