Mercury - Tachometer 8000 RPM SmartCraft Analog Gauge White Face 85 mm 79-8M0069419. Overview. The Mercury Tachometer (79-8M0069419) gives you precise RPM readings so you always know how your engine's performing. It's designed for high-output setups, with a range up to 8000 RPM for quick, accurate monitoring at any speed. The white face, sharp black numerals, and glass lens make it easy to read in bright sun or low light. Built to fit a standard 85 mm (3-3/8") dash hole, it connects directly to