Mercury - Tachometer 8000 RPM SmartCraft Analog Gauge Black Face 85 mm 79-8M0069433. Overview. The Mercury Tachometer (79-8M0069433) gives you precise, real-time RPM readings up to 8000 RPM, perfect for high-performance Mercury engines. With a black face, bold white numerals, and a clear glass lens, it's easy to read in all light conditions and ties in perfectly with other Mercury black-face gauges. It fits a standard 85 mm (3-3/8") dash hole and connects directly to SmartCraft-capable systems f