Mercury - Trim Gauge White Face 2-1/8" (52 mm) 79-8M0052870. Overview. The Mercury Trim Gauge (79-8M0052870) shows your engine trim position at a glance, giving you better control and smoother performance on the water. With its white face, bold black markings, and glass lens, this gauge matches other Mercury OEM instruments for a clean, factory look. It fits a standard 2-1/8" (52 mm) dash hole and connects to compatible SmartCraft systems when trim sensors are installed.. Key Features. Trim Posi