BD take the ducer that came with it. Next time out when it starts that,unplug the connector for US2 and hook up regular ducer, just hold it over the side of boat and see if it does the same thing. Also go into menu and look for transducer options. I think there may be a option for the a universal transducer just can't remember what it's called. Friend has a 788 hooked to his and never had any problems.