Someone out there may have interfaced SeaTalk directly to their PC, but I'm not sure what software
you could use to decode it. None of the ST60 instruments I have (wind, depth
, speed) have a NMEA output. As far as I know to get NMEA output from Raymarine you need another device on the SeaTalk bus. Raymarine has a SeaTalk to NMEA conversion box. A ST60 Multi-Function display also outputs NMEA as do most of their autopilots. There are also 3rd party conversion boxes (e.g., Brookhouse Mux). Given that 3rd parties have decoded and converted SeaTalk you would think there is a software package that would do it, but when I Googled for SeaTalk conversion I only got hardware
products. Doesn't mean there isn't a product out there, but it doesn't appear to be easy to find.
FWIW, I use a Brookhouse Mux to send SeaTalk data to my PC.