Mercury - SC1000 Tachometer 4000 RPM SmartCraft Analog Gauge Black Face 85 mm 79-8M0135630. Overview. The Mercury SC1000 4000 RPM Tachometer (79-8M0135630) combines SmartCraft accuracy with a clean, factory look. Featuring a black face, white numerals, and a glass lens, it fits a standard 85 mm (3-3/8 in.) dash hole. This tach delivers smooth, real-time RPM readings and supports SmartTow and other SmartCraft features depending on your engine setup and sensors. It's built for boaters who want pre