Humminbird 195c problem

Took my boat out for the first time this weekend. While out I turned on the fishfinder and it kept giving me ridiculous depths, turning off, saying there was no transducer connected and going into simulator mode. I finally just shut it off. Anybody else have these issues? I got it on EBay so I can't return it even though it was new in an opened package. Also, there was a huge rooster tail coming from the transducer when cruising across the lake. Is that normal?

Incorrect and/or rapidly changing depth readings at speed are usually a problem with the transducer's location. Rooster tails are either incorrect transducer location, or it's just the way it is on some HB transducers (but there are DIY fixes for that).

Shut down and simulator are usually a power supply issue, but might possibly be the transducer location problem too.

I'd start with relocating the transducer, which is just getting it close per HB's instructions and then lots of tweaking. It will be much easier if you install a transducer board instead of having to keep drilling into the transom. There's several posts on here about transducer boards, just do a search.