Im thinking of picking this unit up for m canoe. I fish only small water useing a 30lb trolling motor. How much power do you think the unit draws? I only have one battery in he boat "marine type" to run the trolling motor. Would i be safe to hookup the finder to the one battery or will i drain the battery out?

I was thinking i could maybe get a 12v rechargeable from radio shack and have it just for the fishfinder.