Mercury - SC1000 Single Gauge Kit 80 MPH Speedometer Black Face Includes Harness 79-8M0137551. Overview. The Mercury SC1000 Single Gauge Kit (79-8M0137551) includes everything you need to add or replace a speedometer in your SmartCraft-equipped boat. This kit comes with an 80 MPH SC1000 speedometer (black face, glass lens) and the correct SmartCraft harness, making installation simple and clean. It provides accurate, real-time speed readings while keeping that factory Mercury look and feel.. Key