Mercury - SC1000 Speedometer 50 MPH SmartCraft Analog Gauge White Face 85 mm 79-8M01356244. Overview. The Mercury SC1000 50 MPH Speedometer (79-8M0135624) delivers accurate, reliable speed readings with that classic Mercury look. It's built for SmartCraft systems and fits a standard 85 mm (3-3/8 in.) dash opening. The white face with bold black numerals and a glass lens gives it a clean, OEM finish that's easy to read in any light.. This gauge also supports RPM- and speed-based SmartTow function