Mercury - SC1000 Speedometer 80 MPH SmartCraft Analog Gauge Gray Face 85 mm 79-8M0135654. Overview. The Mercury SC1000 80 MPH Speedometer (79-8M0135654) delivers clean, precise speed readings with a sleek gray-face design that looks right at home on any dash. It fits a standard 85 mm (3-3/8 in.) gauge opening and connects directly to your Mercury SmartCraft system for smooth, accurate data. With a glass lens, white numerals, and classic styling, this gauge is both tough and easy to read - whethe