Mercury Marine Product Information This Mercathode Kit 98869A17 is one of the many available in our large selection of Mercury Marine boat engine parts online. Our online boating store is the number one Mercury engine parts source which makes it extremely easy to find the exact engine parts you need. You can also check out our online to search all Original Equipment Manufacturer OEM boat parts today! Most Mercury Marine boat parts are in stock and ready to be shipped to you.The MerCathode system provides automatic protection against galvanic corrosion. It is a solid-state device that operates off a boat's 12-volt battery and provides protection by impressing a reverse blocking current that stops the destructive flow of galvanic currents. If your power package does not come already equipped with a MerCathode system, Mercury strongly recommends that you install one, particularly if your boat is equipped with a stainless steel propeller or other submerged stainless steel hardware.