I have a humminbird 587ci for my boat. I have a humminbird ice35 for on the ice. My question is I would like to use the gps in the 587ci on the ice. Since I have most lakes I icefish on a sd card. The power cord from the ice35 fits the 587ci, and the transducer cable fits as well. However when I power up the 587ci on the screen, it reads tranducer not connected and goes into simulation mode. Is this because I am far away from anylake on the card, or does the proper transducer have to be connected for the GPS funtion to work. Thanks, I love this board.