Depthfinder Question

My buddy has what i believe is hummingbird depth finder (not sure if that is right or not) but it is going a little nuts on us. It is on in I/O on the rear but the problem is that it keeps telling us that we are in 180' water when in reality it is like 20'. Any ideas on how to fix/alleviate this problem?

Have you checked hummingbird's website? I think there is a way to calibrate them, but I couldn't tell you how. Sorry, good luck.