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Readying your boat for winter storage

The whys and hows of winterizing, from treating the fuel to covering your pride and joy

The whys and hows of winterizing, from treating the fuel to covering your pride and joy

Anyone who has owned a boat for more than a year is familiar with the litany of decommissioning tasks required for off-season storage. Some, however, may not be familiar with the reasons for some of these activities. Other, newer boaters may stand to benefit from a few of the tricks and shortcuts that more experienced owners have learned over the years.

The list of generic chores includes winterizing fuel and water systems, changing lubricants and filters, cleaning and storing fabric items, preventing the formation of mold and mildew, and protecting the boat from the elements during storage. This also is a good time to record any problems you encountered during the season, maintenance issues that haven’t been addressed, and indicators of potential problems you run into while decommissioning. The list will help keep the issues in mind so they don’t pop up as surprises in the spring.

Fuel system

Broadly speaking, this involves cleaning or changing fuel filters, and adding a stabilizer to the fuel to preserve its volatility and prevent the formation of sludge while in storage. Although this is a fairly straightforward operation, the are a few steps you can take to make sure your efforts result in the best outcome.

• With an inboard or outboard, stabilize the fuel first so that any subsequent operation of the engine will get the stabilizer through the system. I also like to put some stabilizer in the fuel filters to expedite its getting into the system. Many experts suggest filling the tank completely to reduce the formation of condensation during storage. However, if you use gas that contains ethanol, you might want to consider drawing down the tank as far as possible because the ethanol will hold any water that’s in the system.

• Consider winterizing the fuel system first or integrating those activities with the oil change to avoid excess engine operation on its new oil (see below).

Lubricant and filter changes

Regularly changing oils and lubricants in engines, transmissions and drive units is a necessary part of normal maintenance, but it is especially important in preparation for winter storage. Once used for even a short time, engine oil becomes contaminated with microscopic bits of metal produced by normal wear, and by the corrosive byproducts of combustion. Leaving used oil in an engine for an extended storage period can allow the pollutants to settle into a hard-to-remove sludge and let the acids damage sensitive surfaces within the power plant.

The gear lubricant in outboard and sterndrive lower units not only collects abrasive metal bits but is susceptible to contamination by water, as well. Changing it is a must.

There are several things you can do to make oil and filter changes easier and more effective.

• Begin by loosening spin-on oil and fuel filters mounted directly to the engine while the engine is still cool. Back them off just to the point where they can be removed without a wrench but not so far as to allow leaking. This makes them much easier to deal with after the engine is warmed.

• Run the engine long enough to raise the temperature of the oil. This makes the oil easier to pump or drain, and ensures that contaminants are suspended in the oil and will come out with it, rather than remaining settled in the oil reservoir. After shutting off the engine, wait for its oil to drain back down into the pan or reservoir to ensure that the maximum amount of old oil is removed.

• For spin-on filters that use replaceable cartridges, wipe any residue from the bottom of the canister so that it doesn’t end up in the new filter.

• After refilling with new oil, run the engine only long enough to check for leaks, if possible, to avoid contaminating the new oil.

Water system

The primary objective in decommissioning potable and cooling water systems is to prevent damaging freeze-ups in colder climates. The surest way to do this is to completely drain all water from the systems. However, it isn’t possible in many cases, so the addition of antifreeze is the safest and most reliable method of prevention.

Unfortunately, the level of protection offered by antifreeze solutions is often misunderstood. The quoted level of protection — “down to -50 F” — is derived from residential construction standards and is intended to mean that copper pipes will burst when the antifreeze in them reaches that temperature. The “-50 F” is a failure point, not a protection point.

The danger is that the plastic pipes, filter housings and pump bodies in marine use will be destroyed long before that level, so the type and strength of the antifreeze solution you choose is important. You must assume that some water will remain in the system to dilute the antifreeze and raise its freeze point in the process. The extra cost (about double) of “-100 F” antifreeze can be inexpensive insurance.

Here are some other overlooked considerations.

• Drain as much of the water from the system as possible before adding antifreeze to avoid diluting it unnecessarily. (Make sure the boat is as level as possible so tanks will drain completely.) This is especially important for water heaters, which are usually equipped with a check valve in the water inlet that prevents draining back into the system. Most are equipped with a separate outlet that allows complete draining.

• Pump antifreeze through every outlet on the boat to ensure each line is protected. Once the color of the flow indicates that antifreeze is coming through, redirect it to a bucket. The overflow can be recycled back through to reduce the amount of antifreeze required or used to protect deck drain plumbing, and areas where water remains in the bilge and holding tanks.

• Don’t neglect the shower sump. It should be cleaned with a bleach solution to cut soap scum and kill off any bacteria, then filled with antifreeze that can be run through to protect its pump and drain system.

Canvas cleaning and storage

Fabric manufacturers will tell you that the best way to maintain their products is to prevent dirt from building up in the first place. Hosing down covers and enclosures with cold water on a regular basis can eliminate much of the need for harsh cleaning at season’s end. But all fabric items should be cleaned before storage. Grit that remains can abrade fabric fibers. And salt crystals not only cause abrasion but attract moisture, inviting mildew and more.

Here are some pointers in caring for fabrics.

• Synthetic fabrics like Sunbrella can be washed with detergents when necessary, but repeated washing reduces their water resistance, which is the result of a coating applied at the factory. If this happens, applying a product like 303 High Tech Fabric Guard should restore the fabric’s water resisting quality.

• Fabrics must be thoroughly dry before storing, especially if they are to be folded. They should be kept in a cool, dry place and protected from rodents and insects.

• Panels with clear plastic windows should be stored so that no two plastic surfaces rub together. Sections of cloth — old bed sheets work well — placed between them will prevent scratching and hazing. They should never be stored in plastic bags.

Mold and mildew

Mold and mildew are fungi that reproduce by spores that waft through the air. They thrive in damp, unventilated areas but are easy to avoid through cleanliness and ventilation.

All surfaces that may have come in contact with food or drink should be thoroughly cleaned with a fungicidal agent such as Lysol, or a solution of bleach, detergent and water. Coolers and refrigerators are prime targets for mold and mildew, and should be cleaned and propped open for ventilation during storage.

Protection from the elements

Short of indoor storage, the most successful off-season cover is one that protects the boat from precipitation, dirt and damage while allowing sufficient ventilation to prevent mold, mildew and musty odors. Plastic shrink-wrap over a stout wooden frame seems to be today’s solution of choice, but it must be properly installed and outfitted.

Keep in mind that boats that are painted (Awlgrip, etc.) should be shrink-wrapped carefully to ensure that the wrap, its seams and tie-downs don’t come in contact with painted surfaces, which could be damaged by abrasion as the cover moves in response to wind and temperature changes.

Since shrink-wrap provides such a good seal, make sure the installer provides screened vents facing in all directions to facilitate airflow. You’ll want to have a door installed, as well. This way you can board after the boat is wrapped and open as many ports and hatches as possible for ventilation.


• Many manufacturers recommend engines be fogged as a last shutdown operation. Carbureted and electronically fuel-injected engines have different fogging methods. Fogging a carbureted engine involves introducing a spray or stream of oil into the engine through the carburetor. The object is to provide the cylinders with a protective coating during storage.

You can fog your carbureted 2-stroke by spraying fogging oil through the carburetor until the engine stalls. But for EFI 2-strokes and 4-strokes and carbureted 4-strokes, you must consult the manual because some can be fogged, and some require an oil mixture be put in the fuel filter or in a separate tank.

• Don’t forget the batteries. Their safest haven in cold climates is indoors. While a fully charged battery generally won’t freeze until the temperature nears -40 degrees F, one that is 50-percent depleted can freeze at 15 degrees F. Since there are few things messier than a lead-acid battery that has burst, it’s prudent to err on the conservative side.

• The last task on the decommissioning list should be a review of your owner’s manuals — engine, generator, boat, etc. — to check for winterization requirements that may be particular to your situation. Getting ready for storage is a lot of work, but when it’s properly and thoughtfully done, the decommissioning process leaves you with a well-protected boat and a lot less to worry about come launch day.