What i have is two graphs on the back with their own transducers. They are a hds 7 and hdi 7. I'm having problems with the hdi 7. The hdi thats mounted on the front works no problem. I took it out today and used a different frequency and it cleared the picture up. However, once i got on plane then went back down to an idle it would never relocate the bottom. Most of the time i had to restart the graph before it would. Worked great once it found bottom. But once I lost bottom from driving it would never relocate it. Just kept saying 1.2ft or 3ft etc.