hi stevi, welcome to sealine. i don't know anything about trolling motors and things like that, in fact i think you'd probably do better trying the bass or general freshwater section, but i do recall seeing a fishfinder that can be mounted on a canoe...don't ask me where i saw it, probably in a magazine, but try any reputable tackle dealer, they can probably put you on the right track.
ps. nie om onbeskof te wees nie, maar ek dink meeste ouens op sealine is engels, so try miskien in engels post, dan sal jy dalk meer responses kry.
cheers,
PC