[rgmori]

I recently aquired a cable for the Garmin 72 with a USB to Serial converter. The signal lines were on pins 2 and 3 with the ground on pin 5 and the positive on pin 9 of the 9 pin serial connector. This would allow a hookup to a NMEA system aboard a boat with an external power source. The external power source should be rated at 8 to 35 volts DC.

The MTC USB to serial converter software driver requires a minor hack in the terminal for OS 10.3x and above.
http://www.mct.com.tw/driver.html
in the terminal after root user is enabled type:
sudo su then hit return
enter your user password and hit return
now type:
chmod -R og-w /System/Library/Extensions/USBSerialDriver.kext
hit return
then type:
chown -R root:wheel /System/Library/Extensions/USBSerialDriver.kext
hit return and quit the terminal
reboot and the driver works properly. You may now use the Garmin 72 with GPSNavX.