Mercury - Tachometer 7000 RPM SmartCraft Analog Gauge Gray Face 85 mm 79-8M0065981. Overview. The Mercury Tachometer (79-8M0065981) gives you a clear, accurate look at your engine's RPMs, helping you stay in the optimal range for performance and efficiency. With a range up to 7000 RPM, this gauge is built for versatility - ideal for outboards, sterndrives, and performance setups. The gray face, sharp white numerals, and glass lens make it easy to read in any light, while the 85 mm (3-3/8") fit e