I have been living with the same problem with our C80 . On our boat we have a Raystar Seatalk GPS unit.
I will need to remove the saloon ceiling liner (big tedious job) to gain access to the Raystar mounting screws before pulling it apart to see if it is possible to fit a new battery.
Can anyone confirm if the seatalk version has a battery that can be replaced?
It would be far easier to fit a new nmea wire tailed gps mushroom and break into the existing nmea connections. This could also provide a lat long for the DSC radio.
In my case I am considering adding an ais transponder which can replace the Raystar as a primary gps source for the C80. Probably need to do this anyhow as the C80 will only communicate at the higher baud rate as I think it has a mono speed nmea input output channel.
