I have a Simrad ST20 AutoHelm hooked to a Garmin ETrex GPS and it
works quite well, but it requires me to manually reset the autotiller
at each waypoint change. When a waypoint is reached the tiller
'disconnects' from the the GPS and, if I don't reconnect by pressing
the tiller Navigation button, it just continues on the last course --
i.e. it doesn't move on to the next waypoint in the list. The
TillerPilot does let me know that it is going off line by beeping, but
between outboard noise and my poor hearing I sometimes don't hear it.

I wonder if this is normal behavior or if I am missing something.
Neither Garmin nor Simrad give much information about hookup or
operations in the NMEA mode. Any pointers appreciated....

Otherwise the setup is great fun and makes some of the long runs under
the "iron wind" quite livable.

Rye WWP19 -- Potomac River/Washington DC area (WSM)