Don't know if this would work or not. I use plumbers putty for my transducer. You might try and use it. I would put a 1/4 inch thick on the bottom, press the battery box into it and then build up the sides to keep it in place. Never tried it for something that size but it sticks to the bottom of my yak and doesn't come loose. The best part is, if it doesn't work or you want to relocate the box, it will peel right off. About 2 to 3 bucks at home depot.
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