fishfinder freezes/shuts off

[awcjfk]

hi, i have a hummingbird wide 100 for the last several years. last year and this year the fishfinder freezes sporatically. when this happens i cannot turn unit off, so i have to remove the head and put it back on. than press the power button to get it working again. i also notice in addition when i start the engine (when the unit is on), the fishfinder turns off and i cannot turn it on without removing and replacing the head. i put a new head unit on and the same problem. i check the wires as much as i could and so far have not found any problems. anyone have a problem like this? do you think i should try to run the hot wire directly to the battery (with an inline fuse) and see what happens? appreciate any advice, suggestions. thanks john