Mercury - Quicksilver 821631T1 Aluminum Gimbal Housing Anode MerCruiser R, MR, Alpha One Gen II, Bravo, X, XR & XZ Drives 821631T1. Overview. Your sterndrive lives in one of the toughest environments on your boat - submerged metal, saltwater, and constant current flow. The Mercury 821631T1 Aluminum Gimbal Housing Anode is designed to take the hit so your drive doesn't. This OEM anode protects your MerCruiser R, MR, Alpha One Gen II, Bravo, X, XR, and XZ drives from galvanic corrosion, extending