In my area, I drain the salt water side of the exchanger by pulling the zinc after closing the seacock. But we rarely drop below freezing for very long. In very cold parts of the country, it is recommended that you run the engine and pull the pink antifreeze from a pail through your raw water intake via a hose. When you see the pink stuff exit your exhaust, you know it's all set for winter. And, it's environmentally friendly being propylene glycol (pink stuff) vs. the yellow-green ethylene glycol on the freshwater side.
