I'm in the process of installing a NMEA 2000 Backbone and connecting up my
RayMarine E-Seris and my Volvo Penta engines via the Volvo NMEA GW. In
reading the NMEA spec, it mentions..

"In all cases the power and Common ground for the interface circuits must
not connect to other power or ground in a network"

Does this mean the Power Tap for the NMEA backbone should be on a seperate
switched circuit or could it share a circuit with another device on the
network, i.e. GPS, MFD, etc? Also, can the bared shield drain wire be
connected to the boat's common ground?