Mercury - Upper Driveshaft Bearing Cup Cone Multi-Series Drivetrain Component Marine Alloy 8M0146566. Overview. Anyone who has spent enough time on the water knows that the smoothness of an outboard is something you can feel through the entire boat. When the drivetrain is healthy, everything just responds the way it should - clean shifts, steady thrust, no surprises. The Quicksilver 8M0146566 Upper Driveshaft Bearing Cup Cone is one of those hidden-but-critical parts that keeps that feeling aliv