Mercury - Quicksilver Water Pressure Sensor Engine Monitoring Marine-Grade Construction 881879T11. Overview. Any boater who's spent real time on the water knows the comfort that comes from glancing at your gauges and seeing everything right where it should be. That quiet steadiness - the engine breathing easy, temperatures holding, pressure sitting in that sweet spot - makes every trip feel a little more relaxed. This Mercury Marine part plays a bigger role in that peace of mind than most people