I've got my Garmin GPS 45 hooked up to my Furuno sounder via a NMEA cable to feed the Nav data to the sounder for display purposes. Unfortunately, if I power down the GPS with the NMEA cable connected the GPS will not turn back on...I am forced to disconnect the cable to get the GPS turned back on ...The Furuno manual instructs me to tape off the black & Red wires in the Nmea cable to prevent a short circut...Help??