How To Winterize Your Sailboat

You thought owning a sailboat was going to be all fun and games. That your life was going to be a commercial for a Ralph Lauren cologne. Or a Pitbull music video. Or a combination of both. But now summer’s over, the cold weather is coming and you find yourself stuck with the task of draining your precious vessel of all its vital fluids and scraping zebra mussels off her haul. It’s something Robin Leach never talked about on Lifestyles of the Rich and Famous, but alas, matey, it’s your sad  — and absolutely necessary — reality.

There’s no avoiding the daunting task of winterizing your sailboat, well, not unless you’re interested in some hefty repair bills, poor performance and consequently, less time on the water. Maintenance is a fact of ownership, not to mention essential to the longevity of your vessel. If you decide winterization isn’t for you, you may want to check your insurance coverage as many policies won’t cover repairs caused by maintenance neglect.


Guidelines To Winterizing Your Sailboat

NOTE: Always refer to your owner’s manual first and foremost!

Fuel Tank: Run the engine to operating temperature, checking for leaks. Add stabilizer to the fuel, filling the tank to 95% full – to prevent oxidation and ethanol separation. Replace fuel filter and water-separating fuel filter. Keep the engine running for 15 minutes to circulate and stabilize the fuel. Make sure to follow stabilizer bottle instructions.

Engine Protection: Winterization of your sailboat varies depending on: engine type (inboard, outboard), engine fuel type (gasoline or diesel) and if applicable, inboard cooling systems (raw water or enclosed fresh water). The engine block is vulnerable to freezing if left untouched, leading to cracks and big repair bills – so don’t miss this step! Read your manual for more details.

Inboards: Thoroughly drain the engine by opening up the petcocks. Remove water intake hose, start the engine and bring to operating temperature, then add nontoxic antifreeze (propylene glycol) and circulate by running engine until water comes out the exhaust. Spray fogging oil into the engine and cylinders to prevent corrosion (gas engines). And swap the oil filter.

Outboards: Consult the manual, if it’s under warranty be sure only to use the manuals wintering instructions to ensure you don’t void your warranty. The basic steps are flush out the engine with fresh water using proper attachments. Stabilize gas tank. Run engine, change oil and filter and, then inject fog into the carburetor and cylinders. Also, change the gear case fluid in the lower end of the outboard. This can get some water in it during the run of a season and if the water freezes can be hard on the gears. Also, if the outboard is to be left tilted up, cover the prop opening with plastic and tape so as to avoid gathering water and damage from expansion.

General notes on engine protection: Do not run the motor up to temperature without the cooling system attached. Running the raw water impeller for that period of time can result in “dry run” and damage the flaps of the impeller that draws the raw water in the system; also this would be quite easy to overheat the motor accidentally if not careful. Put coolant through the motor as a last step, only removing the water intake hose when ready to draw in the antifreeze, placing the intake hose in the bottle of antifreeze and watching for it to exit the transom.


While the boat is still in the water, perform the oil change which includes a filter change. The oil change works best when the motor is up to temperature so this is when you should run the motor for several minutes while still in the water and the coolant system is working.

The oil change is best performed in the fall so the corrosive elements gathered in the oil from the season are not left in the cylinders and oil sump for the long winter months. Consider an oil suction container as boats often don’t have a drain at the bottom of the oil sump and oil needs to be removed from the dipstick hose.

Freshwater System: It’s critical to bleed all the water out of the freshwater tanks (hot water and all associated plumbing) then flush out with nontoxic antifreeze by opening outlets like the shower – until antifreeze drains out. Both the hot and cold water systems need draining and you should see antifreeze exit each faucet from the hot and cold.

Marine Heads (toilet): Empty the holding tank at an approved facility (if there is one). For a boat without a holding tank disinfect the bowl, close the seacock and remove the hose, placing into nontoxic antifreeze. Then pump the head full of antifreeze, return the hose. With a holding tank, empty tank, disinfect and then fill bowl/tank via Y-valve with antifreeze. Finish up by closing seacocks.

Batteries: Disconnect the battery, charge it fully and store in a warm, dry place. Charge monthly – just don’t leave on charger.

Interior Clean-up: Clean or fix any/all loose items (sails, lines), unhook any electronics and store somewhere warm and dry, and empty your sailboat of food. Disinfect the fridge and any other surface. Prop open doors – bilge, lockers – to improve circulation and consider containers with dehumidifier material or moisture absorbing products to stamp out the potential of mildew growth. Also, remove cushions and anything that is likely to retain moisture to keep the interior drier over the winter.

Exterior Cleanse: Open all seacocks to drain out water and scrub away any barnacles clinging to the sides of your boat before wrapping your vessel (if applicable). Wash the hull, thru-hulls and strainers. Drain and clean the bilge. Inspect for blistering – repair if need be – then apply a good wax in preparation for next year

Storage: The best way to protect your boat from the elements is to store it in a climate controlled indoor environment – be it your heated garage or an indoor storage facility. This is the best option. If indoor, heated storage is not possible, the next best thing involves storing your boat ashore and custom wrapping your vessel to keep moisture and unwanted pests out.


Maintaining your sailboat for winter storage isn’t thrilling, but it is a necessary evil if you want to hit the water next season without hitch. So do yourself a favour, winterize your vessel. And when the upcoming boating season arrives, it’ll be nothing but smooth sailing ahead.

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