On Tue, 18 Aug 2009 12:05:34 -0400, Armond Perretta wrote:

I have Capn 8.3 running with several GPS units that can be switched to
provide nav data. This setup works just fine and has for a very long
time. I just loaded Offshore Navigator Light and SeaClear II for the fun
of it, and it happens that neither program can "see" the GPS data. I am
using a standard USB-to-serial cable and I have tried just about every
combination of port and speed and GPS interface setting on 3 separate
GPS units, but so far no go. Meanwhile the Capn 8.3 can see anything I
feed it. Any ideas?

The USB-to-serial cable *might* have something to do with it. The USB
standard does not include a GPS device, so a proprietary driver is
needed. Capn probably provides them, perhaps, ONL and SeaClear don't.
If you are familiar with telnet, you could telnet the port and see what,
if anything, is being transmitted.