Depending on how old that 2D Humminbird unit was, the newer Sonar-GPS combo units may have the same or less current draw.
Humminbird (Techsonic Industries, Inc.) was bought by Johnson Outdoors Inc. back in 2004.
Greg, I'm looking seriously at a HB 346c DI and want to mount the transducer (XNT-9-DI-T) on the inside of the hull. I'm getting mixed information on whether it would work with that transducer. I find places that say no and some that say yes. What say you?