I have a one year old 150 four stroke with a mercmonitor level one gauge. I'm looking at hooking it to a simple NMEA 2000 network to show the available engine data. The gauge has a "external power" harness and a fuse hanging off of the back that isn't connected to anything. I'm providing power to the NMEA via the standard power "T". I've read a bunch of stuff but am still uncertain what exactly this gauge harness is used for. Anyone know the right answer? Thanks in advance.