What Is Winterizing?
Before the mercury dips below freezing, you need to prepare your boat for the coming winter.
At its most basic, winterizing means draining any water aboard or replacing it with enough of the right kind of antifreeze to protect against the lowest temperatures your boat might experience. Freshwater expands in volume by about 9% when it freezes and can push outward with a force of tens of thousands of pounds per square inch. That expansion can crack an engine block, damage fiberglass, split hoses, or destroy a refrigeration system overnight.
Recent analysis of 10 years of freeze claims found that more than three-quarters involved cracks in the engine block or the exhaust manifolds that occurred because water remained in the engine or cooling system during a hard freeze. Not surprisingly, those repairs are expensive and time-consuming.
Engines tend to take the brunt of the damage from freezing weather, so they should be your focus. Winterizing engines means draining the water from the engine or replacing it with antifreeze.
Mistakes in this step lead to the vast majority of the freeze claims in the insurance files.
Antifreeze for winterizing engines and freshwater systems is not the same as the coolant you put in your engine's heat exchanger (the boat equivalent of a radiator). Ethylene glycol, the chemical used in coolant, is highly toxic, so winterizing antifreeze must be nontoxic because it goes in drinking water systems and may eventually go overboard. The antifreeze you use in your engine and plumbing systems must also have the proper freeze protection to keep your systems safe at the lowest possible temperatures your boat may face.