Mercury - Quicksilver Low Oil Pressure Switch For MerCruiser Sterndrive & Inboard Engines 805605A1. Overview. When oil pressure drops, you need to know right away. The Mercury Marine 805605A1 Quicksilver Low Oil Pressure Switch is built to do exactly that - sending a signal to your boat's warning system the instant pressure falls below a safe level. Designed for MerCruiser sterndrive and inboard engines, this OEM switch helps prevent major engine damage by giving you early notice before things g