Yamaha - Trim Tab Anode Corrosion Protection 69L-45371-00-00. Overview. The Yamaha 69L-45371-00-00 Trim Tab Anode serves two important functions on Yamaha outboards: helping protect the lower unit from corrosion and assisting with steering torque adjustment. Mounted on the underside of the anti-ventilation plate, the trim tab anode acts as a sacrificial metal that corrodes instead of the surrounding aluminum components.. For boaters running in saltwater or brackish environments, trim tab anodes