The NMEA 2000 power isolator is useful to ensure proper installation of the NMEA 2000 network in separating different power sources that could power the bus. Some NMEA 2000 capable engines can potentially provide power to the NMEA 2000 bus. The NMEA 2000 power isolator is useful because it makes sure the NMEA 2000 power from the engines and system power are kept separate.
NMEA 2000 Power Isolator
Garmin VHF Marine Radios