I have Hummingbird Fish/Depth Finders on the 1990 Ranger bassboat that I just bought. I can only find one transducer located on the rear transom at below the water level. The problem is that they go blank intermittently or don't read the bottom at all. They have power all the time. Should both the front and above dash finders be wired to the same transducer or should there be two transducers? These are both the original Hummingbirds with the boat, circa 1989/1990. Does anyone know anything about the wiring or troubleshooting on these things? Could really use some help if anyone has good knowledge on these. I live in Firestone Park in Akron.