MP,
Is our resident expert on these matters but I'll tell you what I did and show a couple of pics.
I don't know how long the line between the unit and transducer is on your unit. I had enough line I could mount the transducer in the bow, but my method would work in the stern as well, say under your seat?
I just used auto water hose tape but good duct tape would work too to tape the wire to the side of canoe right under gunnel rail. Out of way and won't snag on portages.
My unit came with a mount, but I wanted in easy on/off, so I used a small strap to secure it between the yoke pads. I just loosen it and turn under on portages.
I did a lot of reading about shooting thru the hull on kayak fishing sites. As you can imagine everyone had a different take on how to do it.

I took a couple of ideas that made sense to me and
McGeyvered the rest.
I took a plastic tub (round) with a screw on lid. You need a size that your puck fits into properly. I drilled a hole in it the size of puck wire and cut a slit in the side of the tub so puck will lay right. I took a piece of closed cell foam and cut it to lay on top of the puck and hold it properly plus not rattle around on portages.
Before using unit I fill the tub with water. I read where that helps with shooting thru hull? Don't know if that's true, but it can't hurt.
The tub is secured to the floor of the canoe, say in the bow or under the stern seat with Silicone ADHESIVE ( I wanted it to stick thru the roughest portages.) I made sure the mounting surface was clean and scruffed up a little with sandpaper.
Made a circle around the bottom of the tub, an X inside the circle. Set in place and put a heavy weight on the tub and let adhesive cure.
This will hold it even if you get water in the canoe and you can still remove tub if you want with a sharp putty knife.
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