Yes it will.
If you have one of the older GR16 or GR50 GPS Receivers (or a GRHA), you can get the $GP NMEA sentences by splicing into the cable coming from the GPS Receiver before it gets to the head unit (Green wire for NMEA Output and Bare or Black wire for NMEA Ground).
If you have one of the newer GR16 or GR50 GPS Receivers; the Green wire has been brought out to the NMEA pigtail connector (we did away with the Red wire), so you would not have to splice into the cable to get the $GP NMEA sentences.
Be aware though that the $GP NMEA sentences will not have Water Depth, Water Temperature nor the APB (Autopilot Sentence B), BWR (Bearing and Distance to Waypoint aka: Rhumb Line), or RMB (Recommended Minimum Navigation Information) NMEA sentences either. On the plus side: the data will be outputted at 4x per second and there will not be the 1 second delay in the output of the data as there is if it goes through the head unit.