Starting with a Humminbird PihanaMax 185c, I mounted it on a square of 1/2" marine plywood covered with a scrap of Astroturf left over from when I carpeted my pond boat. Inside the waterproof plastic container is a 12v home security system battery and an in-line fuse holder with a 1 amp fuse. I cut the power cable short to fit better. I couldn't do that with the transducer cable, so I merely folded it up and hold it in place with cable ties and 2 old battery tie-downs. I mounted the trolling motor transducer on an old foam float that came with a kayak brush anchor. I secured a length of parachute nylon alongside the transducer cable for strength, and then placed both inside a piece of split PVC. I'll just "dangle" the transducer in the water over the side of whatever boat I use it on. There's also a safety line to attach to something on/in the boat so I don't lose the whole thing. I now have an extra depth finder that I can use in any boat I fish from that doesn't have one. Not very expensive, either. Total cost was less than $125, including a new PirhanaMAX. Photos below.