Is it still possible to link these two systems and share waypoints as long as I am running two map cards? (I do not know what alphanumeric GPS is)
As indicated above, LightHouse II software does not support use of a/c/e-Series MFDs within an Ethernet network in which additional includes MFDs running LightHouse 3 software. However within a SeaTalkng / NMEA 2000 backbone, it is possible to include a Data Master MFD running LightHouse II software and a Data Master MFD running LightHouse 3 software. When so interfaced, communications between the LightHouse II MFD and LighHouse 3 MFD will be limited (i.e. alphanumeric GPS, depth, instrument, navigation, and system state data) between the MFDs. Chart, radar, fishfinder sonar, camera video, thermal camera, SiriusXM Satellite Weather / Radio resource sharing and other data intensive features requiring Ethernet communications will not be supported by a LightHouse II MFD and a LightHouse 3 MFD which have been interfaced via SeaTalkng / NMEA 2000 communications.
http://forum.raymarine.com/showthread.php?tid=3097