Mercury - Quicksilver 821631Q1 Aluminum Gimbal Housing Anode MerCruiser R, MR, Alpha One Gen II, Bravo, X, XR & XZ Drives 821631Q1. Overview. Corrosion is the silent killer of sterndrives, but you can stay ahead of it with the Quicksilver 821631Q1 Aluminum Gimbal Housing Anode. Cast from high-quality aluminum, this OEM anode fits perfectly at the base of the gimbal housing on MerCruiser R, MR, Alpha One Gen II, Bravo, X, XR, and XZ drives.. It's designed to protect your drive from galvanic corro