Mercury - Driven Gear Bearing Bravo Series Sterndrive Component Precision-Machined Steel 861787. Overview. There's a certain comfort that comes from knowing the heart of your sterndrive is built on strong, dependable parts. When you're trimming up and heading onto plane, or easing into a tight marina slip with currents pushing at you, the last thing you want is uncertainty in your drive system. A solid, smooth-running gear set can make the entire boat feel more predictable and more responsive. T