[GPSNavX]

Yes you should be able to transfer waypoints, routes, and tracks with MacENC a couple of ways:

Directly with MacENC using "Transfer "To GPS..." on the "Waypoints" or "Routes" menu. Make sure Type is set to Garmin and the USB to Serial Adapter port is selected in the GPS panel Settings drawer. Make sure you switch your Garmin from NMEA to Garmin mode.

Or export waypoints or routes to GPX format via "Transfer" "To GPX" file and use the free LoadMyTracks application ..

http://www.cluetrust.com/LoadMyTracks.html

In both cases your Mac will need to be connected directly to your Garmin GPS.

http://www.gpsnavx.com/MacENC/help/