Posted on: September 18, 2015 9:48 am


Cruising around on the open water is a seasonal activity in our mid-Atlantic region, so inevitably you need to get your boat ready for months of winter storage. While we offer winterizing in our marine engine service department, many boat owners take on some or all of the tasks to properly prepare their boat for storage and protect their pleasure craft or commercial boat until the weather is right to once again get it out on the water.

By doing all the appropriate maintenance tasks and inspections before your boat takes some time off, you’ll be freely able to relaunch your boat as soon as spring is in the air. If you love the boating life then you’ll likely enjoy learning how to handle winterizing your boat while gaining even more knowledge about its operation.

The following list covers the most common supplies you’ll want to use to get the job done. You can count on us for all your Cat® Marine engine parts for maintenance and repairs. Depending on the type of boat you own, you may not need this full list of supplies, but you can check your owner’s manual for the recommendations specific to your boat and engine.

Boat Winterizing Supplies

Before you start winterizing your boat, make sure you have these necessary supplies:

  • A few gallons of marine/RV antifreeze (for inboard/stern drive engines)
  • Can of fogging oil spray
  • Appropriate grade of 4-stroke motor oil
  • Recommended oil filter
  • Lower-unit lubricant
  • Transmission fluid
  • Drain plug gaskets
  • Oil suction pump
  • Lower unit lube injection pump
  • Custom or fitted cover
  • Heavy duty tight weave tarp
  • Tarp snaps

Your Quick Checklist for Winterizing

Below is a quick-glance checklist to give you an overview of all the tasks to be done. If you’re a new boat owner, you may need to check out a glossary of boat terms to familiarize yourself with some of the descriptions. Your boat and engine owner’s manual will also have recommendations2_Marine-Parts for winterizing so remember to check your manuals for more direction that may be specific to the design of your boat and motor.

  • Inboard & stern drive engines:
    • Change oil (do this step after engine has been recently run).
    • Flush engine with fresh water then circulate anti-freeze through engine.
    • Change transmission fluid.
    • Spray fogging oil into cylinders and wipe down engine with fogging oil.
  • Outboard Engines:
    • Flush engine with fresh water.
    • Wash down engine with soap and water.
    • Disconnect fuel hose and run engine until it stops.
    • Spray fogging oil in the cylinders.
    • Apply grease to propeller shafts and threads.
    • Change gear oil.
    • Wipe a light layer of lubricate on exterior of engine or polish with wax.
  • Fill fuel tank with fresh fuel and add a fuel stabilizer.
  • Clean bilges with soap and water, and then add some antifreeze.
  • Drain the tank of your freshwater system and hot water heater.
  • Pump a nontoxic antifreeze in the hot water heater and freshwater system.
  • Disconnect the hot water heater.
  • Pump out the holding tank and add fresh water to the bowl, flushing several times
  • Remove all contents from the interior.
  • Thoroughly clean the interior including refrigerator and freezer and remove cushions and store in a climate controlled area or prop up on their sides so air can circulate around them.
  • Prevent moisture and mildew by installing a dehumidifier or use a moisture absorbing product like “No Damp.”
  • If storing out of the water:
    • Pressure wash hull and clean debris off exterior.
    • Open seacocks to allow complete drainage of water.
    • Inspect exterior for any repairs to be done over the winter.
    • Give the hull a good wax job.
    • Inspect battery, clean terminals and store at home with a full charge.
  • If storing in the water:
    • Close all seacocks.
    • Inspect exterior for any repairs and maintenance to be done.
    • Inspect battery, make sure it’s fully charged, clean terminals, add water if needed and store at home with a full charge.
    • Inspect bilge pumps to ensure proper operation.
    • If the water freezes where you’re docked or moored, surround your boat with a bubbling system or de-icing device.
    • Check your boat periodically throughout the winter.
  • Protect with a fitted boat cover and then secure a heavy duty tarp for additional protection.

If you’re a bit more of a seasoned boater, this general checklist should serve as a helpful reminder of all that needs to be done. If you need a bit more direction, here is a more detailed description of each step above.

Cleaning Your Boat Inside and Out

Remove all contents from the inside of your boat, including any valuables, electronics, flares, fire extinguishers, PFD’s, etc.

Thoroughly clean the interior and exterior of your boat using the appropriate marine cleaners. Attend to all surfaces: the deck, cabins, refrigerator, freezer, head, saloon, plastic, glass, teak, hull and every other nook and cranny. While you’re scrubbing and polishing you will have the perfect opportunity to inspect all areas of the boat to determine if any repairs are needed before you store it over the winter or to be aware of what needs to be done in the spring before you relaunch.

Keep all cabinets, drawers and doors open for optimum ventilation. If you can’t take cushions home for storage, be sure to prop them up on their sides for the increased air circulation. Place a few dehumidifiers like Starbrite® No Damp products or mold and mildew gas bags to absorb moisture in the air.

If you’re storing out of the water, pressure wash the hull and clean barnacles from the shafts and props, rudders, struts and trim tabs. Then clean the strainers and thru-hulls and open the seacocks to allow drainage of water. This is also a good time to give the hull a wax if needed.

If you’re storing in the water, check rudder shafts and stuffing boxes for any needed repairs or need for repacking. Use a de-icing device or bubbling system around your boat to avoid damage from freezing water.


Winterizing Your Powertrain

Your boat would be pretty useless without an engine, so give it the quality treatment it deserves for long-term storage. Taking these steps in the order given will greatly reduce your risk of needing costly repairs when you’re ready to get back out on the water. Your engine needs protection from freezing as well as from the detrimental effects of the stale fuel that results from lengthy periods of non-use.

These steps will give you an excellent guideline of what needs to be done, but also give the maintenance section of your engine owner’s manual a read through to see if there are any additional recommendations from the manufacture and to ensure you use the right products for fluids and filter replacements.

1. Fuel

Fill fuel tank(s) to almost full (with a bit of space to allow for expansion) to avoid the collection of condensation in the tank then add a fuel stabilizer to prevent buildup of varnish in fuel lines, filters and carburetor, and to keep the fuel from deteriorating over time. Replace your fuel filter and water separator or drain the bowl and change the elements in fixed mount units.

2. Engine Flushing

For inboard and stern drive engines, winterize the block with a nontoxic antifreeze flushed through the engine to prevent freezing and cracking of the block. Don’t use antifreeze made for vehicles since it is highly toxic and will end up in the storm drains or the waters where your boat is. Use a marine/RV antifreeze for the lowest temperature available. Even if you know your boat will never be around -100F temperatures, you will always have some water left in the block that will dilute the concentration of the antifreeze leaving you with a higher freezing point of protection than indicated on the bottle.

    • Flush the engine with fresh water with the use of water muffs or a similar device that will connect a garden hose to your cooling system – flush until the engine reaches normal operating temperature.
    • Get your jug of antifreeze and an intake hose to connect the antifreeze to the water pump.
    • Put the end of the hose in a bucket or jug of antifreeze.
    • Start your engine and allow the antifreeze to circulate until you see the antifreeze exit the exhaust.
    • Change transmission fluid.

For outboard engines:

  • Flush the engine with fresh water by using flush muffs or the flushing port on the back of the engine.

3. Oil

After the engine has been recently run, remove the oil dipstick and insert the suction hose of the oil pump into the dipstick tube and suck out all the old oil. Replace the oil filter and fill with the appropriate grade of fresh oil. Changing the oil while it’s warm helps to drain out the impurities with the oil. Now you can refill with your manufacturers’ recommended grade of 4-stroke oil.

4. Internal Engine Protection

For an inboard engine, remove spark plugs one at a time and spray fogging oil in the cylinders to treat the cylinder walls and pistons, protecting them from corrosion.

For an outboard engine, with engine running and cowl removed, spray fogging oil into the air intakes on the front of the engine and remove the fuel line from the engine, spraying the fogging oil until the engine dies. This ensures that there is no fuel left in the lines and carburetor that will leave a build-up of deposits from evaporated fuel. Grease the propeller shaft and threads with a water-resistant product and change the gear oil in the lower unit.

5. Exterior Engine

Wipe down the exterior of the engine with a light film of fogging oil.

Flushing and Treating Your Freshwater and Waste Systems

Unless all water is removed and replaced with antifreeze, you risk starting off your next boating season with expensive repairs from freezing.

Follow these steps to winterize your freshwater system:

  • Turn on the freshwater pump and completely empty the fresh water tank and hot water tank.
  • Turn the pump off.
  • Add 4-6 gallons of marine/RV antifreeze to the freshwater tank.
  • Turn the pump on.
  • Turn off all faucets except the one farthest away from the pump. Using the hot water, turn on the far faucet until you see the antifreeze come out.
  • Turn the faucet off and then repeat the above step with the cold water.
  • Repeat this procedure with all the fixtures, working your way towards the pump, including the shower wash-down areas.

To winterize your waste systems:

  • Make sure your holding tank is pumped. Remove the raw water intake hose from the seacock for each head and place in a small bucket with antifreeze.
  • Flush the head to circulate the antifreeze through the lines and to the holding tank.
  • Replace the hose and close the seacock.
  • Make sure that all raw water strainers are purged and filled with antifreeze.

If your boat has a fixed air conditioner or generator, you’ll need to circulate antifreeze through the system in the same manner.

Battery Care and Charging

Inspect your battery to insure it is fully charged and terminals are clean — Add water if necessary. Also test your charging system to ensure it’s working properly, then check any switches to ensure they are turned off and not inadvertently draining your battery. Some boaters have successfully left their battery in their boat, but if you want to be on the safe side you can store it inside on a trickle charge or recharge it every 30-60 days. Don’t ever store a battery on concrete as it will drain the charge and damage the plates.


Use warm soapy water and a stiff brush to clean up any oil spills. Pump out all the water and pour some antifreeze in the bilge to protect from possible freezing.

Covering and Prolonging the Life of Your Boat

Proper protection for long-term storage is important to prolong the life of many components of your boat. A climate-controlled boat storage area is the best place for your boat to be over the winter, but cost or availability may make this an unattainable option. Whether you’re storing your boat on your own property or in a boat storage lot, you’ll want to be sure you’ve got a secure cover on it.4_Prolonging-Life-of-Boat

Get a custom or fitted cover loose enough to allow adequate air circulation for the most effective way to keep out dirt and debris. You’ll also want to prop the cover with battens or support poles to prevent water from pooling. Add additional protection with heavy, tight weave tarp for a better defense against the harsh winter elements. Select a tarp that is wider and longer than your boat and secure with nylon cord through the grommets and use tarp snaps from a more secure fit or to use in place of missing grommets.

Allowing your boat to thoroughly dry out by storing on a trailer, cradle or jack stands is ideal to prevent blistering and to make possible repairs and other maintenance tasks quicker and easier.

If you have a sailboat, remove your sail to store at home where you can clean and repair it if necessary. Unstep your mast to give the standing rigging a rest over the winter and allow for a thorough visual inspection of all components.

If your boat has a Bimini top or canvas, remove these if possible to prolong the life of the material.

Store the boat with the bow high and remove the drain plugs from the transom to allow it to drain. Keep your drain plug with your boat keys or other boating gear to be sure you can easily find it when needed.

Also, take the time to inspect your boat trailer for any needed maintenance and repairs:

  • Check the tires for cracks in the sidewalls and for excessive wear.
  • Test the electrical and wiring system to ensure it is working properly.
  • Inspect the rollers and bunks to ensure proper operation.
  • Give the whole trailer a good cleaning and repaint if needed; check the frame for integrity.
  • Repack the bearings and grease all fittings.

With a few hours of your own time and few inexpensive parts, you’ll have your boat in great shape for an easy and quick launch in a few short months. Your boat is a deserving investment to look after, so don’t skip any of these important maintenance standards. If any or all of the winterizing process sounds like it’s not for you, Alban Cat has a skilled team of technicians that will be happy to help you out with any pleasure craft or commercial marine service. Contact us today to start finding your Cat marine engine parts.

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