ST2000 and TackTick NMEA 0183 Problem

[nssailor]

Hi, 30' keelboat with existing TackTick network (wind, depth, speed, etc.) including NMEA interface. This is linked with a VHF DSC and a Garmin 720 plotter. I installed an ST2000 tiller pilot and fed it initially with the NMEA output from the TackTick NMEA interface (0183). Routes are derived from the Garmin plotter and display correctly (dist, bearing, XTE, etc.) on the TackTick network. However, when getting the ST2000 to steer the route it consistently takes up a course which is about 35 degrees to left of correct heading. I tried adjusting the declination setting in both network and tillerpilot but didn't change anything. (It is about 18 deg West here).

Changed the feed for the ST2000 to the output feed from the Garmin plotter and everything is fine. Problem is that the Garmin doesn't pass through the wind sentence to allow the ST2000 to steer to apparent wind angle so I lose some functionality.

Any suggestions where the problem may lie or how I can get full functionality?

Thanks,
Colin