on my next boat I will install a total furuno navnet system.

this communicates way easy, using the the all-known ethernet protocol
and connections. I even heard (not verrified) that a normal computer
hub/switch could be used to link them all. interfacing with a PC get
lots easier too, but that is becouse i've got maxsea alredy

tip for davidb:
search for a total interfacing sollution, couse shop-attendants don't
know what they are talking about. The attendant that sold me the
instruments said that seatalk and NMEA were the same, only the wires
should be crossed to connect them together :S
I know different now.

for connecting multiple NMEA 0183 instrument, companies are selling
so-called multiplexers (NMEA hubs in computer language). this might
help out, but runs arround 200 euro's cost.

so, good luck to you,
but be sure to inform widley before making choises.