What are Zincs on Boats?

Zincs are the sacrificial anodes to protect the metal on your boat that's in the water namely the "rudder" or outdrive for I/Os from electrolysis. All the metal parts need to be connected so that the current runs through the zincs and deteriorates those first before affecting the prop and other metal. This is a very important maintenance item to check since the cost can be very high for repairs if there's too much corrosion.
Shop for anodes for your boat on West Marine here: bit.ly/2TmqU82