Mercury - Speedometer 80 MPH / KPH SmartCraft Analog Gauge Black Face 85 mm 79-8M0052853. Overview. The Mercury Speedometer (79-8M0052853) gives you smooth, accurate speed readings in both miles per hour (MPH) and kilometers per hour (KPH). The black face, bold white numerals, and glass lens deliver a crisp, easy-to-read display that looks great on any dash. Designed to fit a standard 85 mm (3-3/8") gauge opening, it ties directly into SmartCraft systems for reliable, real-time performance data.