Because of the way I built my trailer bunks, the standard location for a fish finder transducer would not work due to the bunks extending past the rear of the transom. I didn't want to mount it any closer to the motor so I looked at how to mount it inside to shoot through the hull.
I remember someone said they used plumbers caulking to provide a removable transducer bed - if you ever wanted to remove it.
I was unsure this would really work but figured I would try it to find out. I'm really only worried about water depth and not worried about surface water temperature or the orientation of the transducer.
I pre-drilled a couple mounting screws and then kneeded a good clump of caulking. I wiped up the mounting location with IPA and water mix then packed in the wad of caulking and then sunk the tranducer into it and installed the screws to keep it in place.
I only use a small 8-amp rechargeable 12V security panel battery to power my f-finders and for some reason had my doublts if there was going to be enough power to shoot through the aluminum hull and keep bottom at speed. Well to my surprise and pleasure, the unit work absolutely great. It's as accurate as I need, I verified depth best I could in moving water with a rope and weight. It followed bottom structure as I though it would and even marked what could have been fish in a couple holes.
I'm really happy with it and know I'm never going to knock it off when pulling the boat onto shore or onto my trailer. It doesn't look the prettiest but it is effective and practical and I'll definitely mount this way again. Now that I know this works, I'll secure my wires and will mount my battery to keep from sliding around.