What does winterizing a boat mean?
Winterization is the process of protecting a boat's mechanical and structural systems from cold weather damage. Water left in an engine block, water pump, or plumbing line expands as it freezes. That expansion can crack the block, split hoses, or destroy impellers. In Muskoka, where temperatures drop below -20 degrees Celsius in January, any standing water in an unprotected engine is nearly guaranteed to cause damage by spring.
A full winterization covers five systems: the engine, the fresh water plumbing, the battery, the fuel system, and the hull and cover. Each system has specific steps, and the order matters. Engine work first, fuel stabilizer second, battery last.
How is an outboard engine winterized?
Outboard engines are the most common engine type on Muskoka lakes. The process for a four-stroke outboard involves: running the engine with fresh water from a garden hose to flush salt and debris (freshwater lakes still benefit from this flush), spraying fogging oil into the carburetor intake while the engine is running, changing the gear case oil, flushing and draining the cooling system, and running the engine dry so no water remains in the water pump.
Two-stroke outboards follow a similar process but skip the oil change. Older carbureted outboards need the carburetor bowls drained to prevent varnish buildup over winter.
Muskoka Storage offers outboard winterization starting at $185. We bring the flushing setup to the storage facility, so the engine is treated on the day of delivery.
How is an inboard or sterndrive engine winterized?
Inboard and sterndrive engines are raw-water cooled, meaning they pull lake water directly through the block to cool it. All that water must be purged and replaced with antifreeze before winter. The process involves: running the engine on muffs or a flush kit, switching the raw water intake to a bucket of non-toxic antifreeze (propylene glycol, not ethylene glycol), running the engine until the antifreeze comes out the exhaust, fogging the intake manifold with oil, and draining the exhaust manifolds and riser completely.
Inboard winterization is more involved than outboard and carries more risk if done incorrectly. The exhaust manifolds on older iron-block engines are particularly prone to cracking if any water remains. If you haven't done this yourself before, have a trained technician do it. Muskoka Storage offers inboard winterization starting at $295.
What antifreeze is safe to use in a marine engine?
Use propylene glycol-based antifreeze rated to at least -50 degrees Celsius for the raw water system. It is non-toxic and safe for bilge discharge. Do not use ethylene glycol (automotive antifreeze) in the raw water cooling system. It is toxic and not approved for discharge into Ontario waterways.
What does plumbing winterization involve?
Any boat with a fresh water system, a head (marine toilet), a livewell, or a washdown pump needs those systems drained and treated before winter. Fresh water tanks should be emptied and blown out with compressed air. The fresh water pump should be run until it pulls dry. The toilet should be flushed with antifreeze and the holding tank pumped out at a shore-based pump station before storage.
For simpler day boats with no plumbing, this step is not needed. For a cruiser or family boat with a washroom and galley, plan 30 to 60 minutes for this step. Muskoka Storage charges $165 for a full plumbing winterization.
What should I do with the battery?
Remove the battery from the boat before storage. A battery left in a stored boat will self-discharge over winter and may be permanently damaged if it freezes in a deeply discharged state. Store the battery somewhere above freezing, connected to a quality automatic trickle charger (also called a battery tender or float charger). These maintain the battery at full charge without overcharging it.
Muskoka Storage removes and stores batteries indoors for $45 each, and returns them fully charged in spring. This is the most cost-effective way to handle it for most cottagers who don't want to haul a heavy battery home for the winter.
Does the fuel need to be stabilized?
Yes. Untreated gasoline goes stale in 30 to 60 days and leaves varnish deposits in the carburetor, injectors, and fuel lines. Fill the tank to 95 percent (to reduce condensation space), add a full dose of marine fuel stabilizer, and run the engine for 5 to 10 minutes to circulate the treated fuel through the system.
For direct-injection engines, consult your owner's manual. Some DI systems should be stored with less fuel to prevent injector problems. When in doubt, ask your dealer before the end of the season.
What is the best cover for winter storage in Muskoka?
For outdoor storage in Muskoka, professional shrink wrap is the best option. It forms a sealed, breathable envelope around the boat and is built over a support frame that keeps snow off the deck. A properly installed shrink wrap will hold through a Muskoka winter without sagging, tearing, or admitting moisture. For an explanation of the trade-offs, see our guide to shrink wrap vs canvas covers.