Sorry for the late response.
Up north we use them a lot since most of our diving is by kayak. I have one in my Tarpon 160, with the battery wires running to the front and the battery held up by a battery bag. https://www.austinkayak.com/products/26 ... g-Kit.html
Had the same battery for 3 years and no problems, I think I have replaced the wire connections once.
As for the transducer I use a "wet well" or "water bath" pretty much computer foam with a hole to fit the transducer. The wet well should be water proof to hold water and transducer in it. After I launch Ill just use my glove to fill the hole with ocean water. If you would like I can post pictures later on how its set up.
Also a lot of kayak anglers use this method as well.
quick example https://www.youtube.com/watch?v=OOhPylA0WcM