Re: do they work..
I have a 161 that I use when underway, bridge fishing, and faster trolling on my main motor. It does a good job finding fish, and finding fish embedded in structure. When fishing i use it to find schooling fish, their depth, and underwater structure. I have a second finder that I use in conjunction with my trolliing motor (with a wider cone). I fish in fresh water and 100 ft or less.
The gps function on the 161 is good for an inexpensive gps. However the "go to" function guides me over land. I still trying to find out if I'm doing something wrong regarding this.
A fishfinder will not cause fish to jump on a hook, but I think they are invaluable in fishing.