Mercury - SC1000 Tachometer 4000 RPM (No Logo) SmartCraft Analog Gauge Black Face 85 mm 79-8M0135656. Overview. The Mercury SC1000 4000 RPM Tachometer (79-8M0135656) delivers smooth, accurate RPM readings with a clean, no-logo design. Featuring a black face, white numerals, and a glass lens, it fits any standard 85 mm (3-3/8 in.) gauge hole. It connects directly to your SmartCraft network for real-time performance data and supports SmartTow and other SmartCraft features, depending on your engine