CT - I have a thru-hull transducer in my current boat. I was thinking if doing what your doing in my old boat but never got around to it.
I remember being told that it’s all about the bed your put the transducer on and the liquid you fill wet box with. Do some research.
I found this and it may be worth a read
https://www.stowemarine.com/Depth_In_Hull.pdf
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