Marine antifreeze is non-toxic and often contains rust and corrosion inhibitors that protect your engine during the winter. In contrast, auto antifreeze is designed to be used both as antifreeze and coolant for your car engine and can be extremely toxic and environmentally damaging.

two gallons
Antifreeze, A Friend Indeed Thanks. If you’re going to winterize a boat you’ll need around a five gallon bucket and two gallons of antifreeze to protect your engine and all related plumbing.

Winterizing Your Outboard Motor

1. Drain the crankcase oil (Four-stroke motors)
2. Install a new oil filter (Four-stroke motors)
3. Filling the crankcase with new oil (Four-stroke motors)
4. Changing the lower unit gear oil.
5. Stabilizing the fuel.
6. Flushing the outboard with antifreeze.
7. Fogging the cylinders.

How to De-winterize Your Boat

1. Take the Tarp Off. Before you do anything, you need to get the tarp or covering off your boat.
2. Check the Engine.
3. Refill the Cooling System.
4. Check Water Pumps and Thermostats.
5. Check Cables and Hoses.
6. Check Your Battery.
7. Clean the Distributor.
8. Check the Fuel System.

Fill a five-gallon bucket with undiluted non-toxic antifreeze. Have additional antifreeze handy if you know your boat takes more than that or if you’ve never winterized before. You can use any leftovers in the boat’s plumbing systems.

Winterizing a Stern-Drive

1. Drain Residual Water. First, run the engine on a flusher and get it up to operating temperature so that the thermostat opens.
2. Fill with Antifreeze Solution.
3. Drain/Replace Gear Lube.
4. Check the Prop Shaft.
5. Inspect Everything.

Fill the tank with a nontoxic anti-freeze, then pour a very small amount into the bilge in order to protect your engine’s pump. Drain out any remaining fuel from the Volvo Penta engine and be sure to dispose of it properly. Then fill the tank with fuel stabilizer to protect it over the cool months ahead.

You will need to run the engine for around 5 to 10 minutes to ensure that clean water has completely circulated through. While the engine is running, spray some storage oil into the carburetor in order to lubricate all of the moving parts.

Boat Winterization includes draining the engine, but then refilling the engine with propylene glycol to inhibit corrosion, fogging the engine, draining the sterndrive, stabilizing the fuel system, checking the water pump impeller, etc.