Mercury - Fuel Level Gauge Gray Face 2-1/8" (52 mm) 79-8M0065970. Overview. The Mercury Fuel Level Gauge (79-8M0065970) provides an accurate, easy-to-read view of your remaining fuel at a glance. Designed with a clean gray face, bold white markings, and a glass lens, it's easy to read in any lighting and matches Mercury's modern gray-face gauge line. It fits a standard 2-1/8" (52 mm) dash opening and integrates with SmartCraft-capable systems when compatible fuel sensors are installed. Reliable,