[GPSNavX]

If one of the NMEA inputs is going to be an AIS receiver, then one must use the MiniPlex-lite..

http://www.shipmodul.com/en/miniplex-lite.html

Or a Keyspan Adapter can be used...

http://www.keyspan.com/products/usb/usa19hs/

As AIS NMEA data is at 38,400 rate.