Mercury - Waste Level Gauge White Face 2-1/8" (52 mm) 79-8M0052868. Overview. The Mercury Waste Level Gauge (79-8M0052868) lets you monitor your holding tank levels quickly and accurately. It features a white face, bold black markings, and a glass lens for sharp visibility in any lighting. The gauge fits a standard 2-1/8" (52 mm) dash hole and connects to compatible SmartCraft systems when the proper sensors are installed. Simple, clean, and built to last, it's the OEM choice for boats with onbo