They are battery
operated. That is fine as they recharge from a shore powered craddle. On a jet ski it's great because you run out of fuel
before the battery
charge goes dead. I would have to wonder about the range of the transmitter on full sized boat. In a jet ski it's not like you can take a stroll around the bridge deck
and get out of range.
Most marine depth
sounders once installed seem to last a very very long time with little trouble. I'm not sure it's a problem in need of fixing.
Maybe this device might be used as a backup sounder, though the battery issue always seems to come back.