I had exactly the same problem. The output drivers of the GP150 failed, but otherwise the unit seems to work ok, and displays the correct latlon on the screen. As Stephane says, the Furuno system switches automatically to use the latlon provided by AIS on the network, BUT this does not go to the other peripherals like the radios which are fed by the GP150 NMEA outputs directly.
Furuno cannot repair the GP150, and will offer you the newer model - which does not fit in the cutout!
Other options are
1. Configure the Furuno MFD at the chart table to output latlon data on one of its unused data outputs, and wire this to the radios. I did this on Stella as a first step while I waited for Furuno to repair the GP150.
2. Buy a GPS antenna with NMEA outputs and mount it behind the chart table panel. Use this to feed the radios directly. I did this when Furuno told me they could not fix my GP150 output drivers. This gives better redundancy than 1.
Let me know if you have further questions and I can dig out my notes and assist further.
Sent from my iPhone X