Mercury - Water Level Gauge White Face 2-1/8" (52 mm) 79-8M0052867. Overview. The Mercury Water Level Gauge (79-8M0052867) gives you a simple, accurate way to keep an eye on your freshwater or livewell tank level. It's got a white face, clear black markings, and a glass lens for crisp visibility in any light. The gauge fits a standard 2-1/8" (52 mm) dash opening and ties into compatible SmartCraft systems depending on your engine model and available sensors. It's a clean, durable, and reliable a