Quicksilver - Idler Pulley Support Bushing MerCruiser V8 Series Marine-Grade Aluminum 865193. Overview. If you've spent enough time around a MerCruiser engine, you know the serpentine belt system has its own voice. When everything is aligned and spinning true, the motor sounds steady and sure of itself. But when an idler support bushing starts to wear, you hear the change - a faint rasp, a wobble in the belt, a reminder that something small is affecting something big. This Mercury Marine part br