Mercury - Quicksilver Trim Tab Anode Freshwater Corrosion Protection & Steering Aid Cast Magnesium 31640T6. Overview. If you boat exclusively in freshwater, the Mercury Marine 31640T6 Quicksilver Magnesium Trim Tab Anode offers the best possible protection for your engine and drive. Designed for Mercury and Mariner outboards (35HP and above) and MerCruiser sterndrives (except Bravo), this anode shields vital components from galvanic corrosion while also helping balance steering torque. Made from