I recently replaced the very old motor on my boat with a 2015 Mercury. To do that I had to install a new control box (throttle) and wiring harness. I also purchased a SC1000 multi-mode gauge to monitor all of the engine functions. As I recall, there was a wiring harness from the control box to the SC1000. There were also a number of color coded wires I did not use that were available to connect to other conventional gauges (e.g., a volt meter or water pressure gauge). None of the paperwork that came with new engine and control box told how to connect those wires. I had to call a Mercury tech and ask about them to verify that I didn't need them for my application. Mercury would prefer that I take tthe boat to one of its dealers and let them charge me for the work. .... I will be surprised if the information you want is available anywhere other than from a Mercury tech.
