Winterization Guide: Protecting Your Boat Through an Ontario Winter

Why Ontario Winterization Is Different

Ontario isn't Florida. We get -25°C nights, freeze-thaw cycles that crack engine blocks, and ice that will crush a hull left in the water. Proper winterization is not optional — it is the only thing standing between you and a $15,000 engine replacement bill in the spring.

October: The Haul-Out Window

The ideal haul-out window for most of Ontario is Thanksgiving weekend through the last week of October. Northern lakes (Muskoka, Parry Sound, Nipissing) should be hauled by early October.

Step 1: Engine Winterization (Outboard)

1. Run the engine in a flush bucket with fresh water.
2. Stabilize the fuel: Add marine fuel stabilizer to the tank and run the engine for 10 minutes to circulate treated fuel through the entire system.
3. Fog the engine: With the engine running, spray fogging oil into the carburetors or throttle body until the engine stalls from the excess oil. This coats the cylinder walls with a protective film.
4. Change the lower unit oil: Drain and replace. Milky oil means water intrusion — the seals need replacement.
5. Disconnect the battery: Clean the terminals, apply anti-corrosion spray, and store indoors on a trickle charger.
6. Trim down fully: Store the engine in the fully down/tilted-down position to prevent water pooling in the exhaust passages.

Step 2: Engine Winterization (Inboard/Stern Drive)

1. Flush the cooling system with non-toxic antifreeze rated to -50°C.
2. Change engine oil and filter — used oil contains acidic combustion byproducts that corrode bearings over winter.
3. Fog the engine through the flame arrestor.
4. Drain the exhaust manifolds and risers — the #1 failure point on inboard engines in cold climates.
5. Close the raw water intake seacock after draining.

Step 3: Fresh Water System

• Drain all water tanks, hot water heaters, and lines.
• Pump non-toxic RV antifreeze through every faucet and the head until it runs pink.
• Leave all faucets in the open position to relieve pressure.

Step 4: Hull and Interior

• Wash the hull thoroughly — remove all growth, scum, and waterline stains. Pressure wash the running gear.
• Clean the interior completely — remove all food, fabric cushions, and anything that can absorb moisture or attract rodents.
• Install moisture absorbers (DampRid or equivalent) throughout the cabin.
• Leave all hatches, lockers, and drawers slightly open to promote air circulation and prevent mildew.
• Mouse-proof: Place dryer sheets and mousetraps strategically. Plug any openings with steel wool. Mice will destroy wiring in a single winter.

November - March: Storage Monitoring

• Check monthly for water intrusion, cover damage, and rodent activity.
• Maintain battery charge — a dead battery in winter means a sulfated, destroyed battery in spring.
• If shrink-wrapped: Ensure ventilation flaps are intact. A perfectly sealed wrap creates a humidity chamber that breeds mildew.

April: Spring Commissioning

• Reverse every winterization step in order.
• Inspect all hoses and clamps — rubber degrades when cold. Replace anything cracked.
• Check the trailer — wheel bearings, brake pads, tire condition, and lighting.
• Test all electronics — GPS, depth finder, VHF radio, navigation lights.
• Confirm your registration is current and numbers are legible. Order replacement lettering if needed.

Pro Tip from the Ramp: The first warm weekend in April produces the most frantic, poorly prepared launches of the year. Take your time. A 30-minute systems check prevents a tow truck call on the 401.