Mercury - Complete Gearcase SeaCore Bravo Three XR Series Hard-Coat Anodized Alloy 8866J07. Overview. There's a certain calm that settles in when your boat responds exactly the way you expect - that smooth lift onto plane, the quiet push as the props bite, the confidence that your sterndrive is doing its job without complaint. When you spend your weekends chasing horizon lines or weaving through tight channels, you come to rely on the parts beneath the surface more than anything else. The Mercur