Mercury - Zinc Trim Tab Corrosion Protection & Steering Balance Marine Zinc Construction 853762. Overview. There's a quiet kind of satisfaction in a boat that runs straight and true - no pull, no fight, just smooth control through the throttle. The Mercury Quicksilver 853762 Zinc Trim Tab makes that happen. It's a small part with a big job: balancing your steering and protecting your outboard from corrosion in some of the harshest environments on the water. Built with the same precision and care