I use the cheapest Canadian tire fishfinder
Had an Eagle fishfiner once. The rubber face stuck the buttons too often, so I switched. Get a spare. You can't often get them repaired in the tropics. Tape two 6 volt dry cells together and you can sound an entire area from your dinghy
,or scout out a pass before going thru.
The fuse kept getting disconnected, so I soldered wires onto the ends of a fuse. Contact guaranteed now.