Winterizing Your Boat

April 20, 2020


Properly winterizing your boat will virtually guaranty a smooth Spring recommissioning.— You will need to choose if you are going to store your boat in or out of the water, either way, the boat should be WINTERIZED. — If you are not going to do the job yourself, you need to choose a qualified professional to perform these tasks. Be sure and get in writing what they are going to be doing to prepare our boat for its Winter slumber. — It is important to note that your insurance policy may not cover damage done by lack of maintenance or neglect, which includes proper WINTERIZATON.

The following are basic WINTERIZING procedures which should be performed on any boat that will be stored for more than 2 months— even if it will not be subjected to freezing temperatures. Individuals should refer to their owner’s manual or contact the manufacturer for complete instructions on WINTERIZATION.

These tips are not intended to be all inclusive of the steps necessary for WINTERIZATION, they are intended for informational purposes only.


  • Run your engine to warm it up before changing the engine oil and oil filter
  • This would be a good time to change the transmission fluid also, if equipped
  • Remove spark plugs and spray cylinders with fogging oil
  • Open all block and manifold drain petcocks. Once the water is drained, close the petcocks and fill the engine through the thermostat housing with NON-TOXIC antifreeze (available at marine and RV centers)
  • If your engine is cooled by a closed cooling system, check the concentration and condition of the coolant in the system. If it appears dirty, this would be a good time to convert to an environmentally friendly antifreeze (available at most marine and RV suppliers)
  • Wipe down the engine with a light lubricating oil to protect it from corrosion
  • Fill fuel tanks and add stabilizer
  • Change fuel filter(s) and water separator(s)


  • Inspect the outdrive housing for damage and clean off any growth
  • Drain the gear oil and check for signs of water (milkshake color or streaks) or metal particles
  • Remove outdrive and service u-joints, and gimbal bearings (follow manufacturer’s recommendations)
  • Inspect bellows for weathering, deterioration, or holes. Remount the outdrive and refill with fresh gear lube.
  • Grease all fittings
  • Check fluid levels in steering pumps and trim/tilt pumps
  • Lower the outdrive housing, remove propeller (this is a good time to have it repaired if needed), cover the propeller shaft and rear of housing with plastic and secure. This will help keep wildlife and water out of your outdrive’s cavity


  • Flush engine with fresh water
  • Disconnect the fuel line and let the engine run until it stops
  • Remove the spark plugs and spray fogging oil in the cylinders
  • Drain gearcase and check for water (milkshake color or streaks) or metal particles. Refill with fresh gear oil
  • Fill fuel tank and add fuel stabilizer
  • Change fuel filter and water separator


  • Clean bilge with soap and water, then make sure it is thoroughly dry
  • Remove bilge drain plug (only if storing out of water), and make sure the drain hole is clear of any obstructions


  • Drain entire system including the tank and water heater (if equipped)
  • Pump NON-TOXIC antifreeze through the system, including the water heater (check your owner’s manual for proper procedure)


  • Pump out the holding tank at an approved facility
  • Refer to the owner’s manual for recommendations for acceptable cleaners and approved antifreeze
  • Shower sumps should be cleaned and filled with NON-TOXIC antifreeze


  • Back pump NON-TOXIC antifreeze from the discharge outlet until it runs out the thru-hull fitting.


  • Remove all personal items, electronics (including TV, VCR, and navigational units) and anything loose or easily transportable. Take as much out of the boat as possible. This will prevent damage to those items from mildew or loss from theft. Store in a climate controlled facility. This would be a good time to have any repairs done or have the items cleaned.
  • Clean interior
  • Open all drawers, lockers, and excess panels
  • Either turn cushions up on end, or better yet, take them home
  • Open and clean the refrigerator and freezer
  • Remove any fuels or flammable cleaning products
  • To help keep the moisture down inside the boat, a moisture absorber should be installed (available at most marine centers)
  • Disconnect water line to any icemakers and drain any remaining water out
  • Drain all appliances that use water
  • Check and clean all electrical connections—coat or spray with electrical protectant

STORED OUT OF WATER (recommended)

  • Pressure wash hull
  • Clean barnacles off any machinery parts
  • Clean thru-hulls and strainers
  • Open sea cocks and let the water drain out
  • Check for blisters or damage to gelcoat. Fix them right away, don’t delay
  • Wash entire boat and put a good coat of wax on it
  • Remove batteries and store in a warm environment. Either put on a trickle charger or check and recharge monthly. This would be a good time to clean the terminal ends
  • Remove the bilge drain plug (if equipped). It is recommended to store it in a location that is in plain sight (i.e. attached to the steering wheel). This will hopefully prevent the boat from being launched in the Spring without reinstalling it


  • Close sea cocks (post warning sign to prevent someone from operating the boat without opening them), check for leaks (repair any leaks immediately), check propeller shaft and rudder stuffing boxes for leaks (repair immediately)
  • Check batteries to be sure they are fully charged. Clean connections if necessary
  • Check charging system operation
  • Check bilge pumps and auto float switches for proper operation (repair and replace if they are found inoperable)
  • If your area is subject to freezing temperatures, be sure to have a de-icing device installed in your slip to prevent the water around the boat from freezing which could crush the hull


  • Clean and wax boat, be sure all surfaces are dry before covering
  • Cover the boat with a properly fitted cover. Be sure to provide adequate support structure inside to prevent puddling of water and allow shedding of rain and snow
  • Provide proper venting to prevent moisture buildup which will cause mold and mildew
  • It is important to check the boat periodically (i.e. weekly, bi-weekly), to be sure the cover stays in place
  • Check the boat immediately following any type of storm. Clear anything that may be on top of the cover. Pull the cover up and check for any signs of water in the boat—especially in the bilge. Check the bilge drain to be sure it is clear of any debris. Should you find any damage, if minor, repair immediately. If it appears major, contact your insurance carrier for direction. If you delay repairing the problem, it will more than likely get worse
  • If possible, on a warm, sunny day during the winter, go to the boat and remove the cover, letting the interior vent

There are a number of qualified marine centers that would be happy to provide WINTERIZATION service for a fee. Consult your local directory or contact a marina in your area for further information on WINTERIZING.

These tips are for informational purposes and not intended to be relied upon for use without consulting the procedure that your specific manufacturer or owner’s manuals may recommend. Always follow the manufacturer’s recommendations when performing any maintenance or repairs.