I know you can download them on a SD card and then load them on the other unit. Maybe someone can tell you how to save the waypoint from the other unit. I just turn the sonar to off position on the other unit by pressing the on off button the screen comes up to change backlight setting and background color as well as sonar(transducer) on off button. This way the waypoints and mapping is still working but the sonar(transducer) is not on interfering with the other unit but the waypoints are all on both units.