what I did
After much consultation on the web and elsewhere, I took a sandwich bag, filled it with water, put the transducer inside and moved the bag around to find a good spot. I ended up putting the transducer in the rearmost locker on the starboard side of my Hunter 23. To install it, I bought a wax ring for toilets, scooped out (by hand) enough wax to set the transducer in, with about 3/4" extra on all sides and about 1/4 - 3/8" underneath, and set the transducer in the wax. Then I twisted the transducer around slightly and pushed down on it to get a good seating. It works fine, except when the starboard side hikes up above 25-30 degrees. The hull below the transducer is no longer in contact with the water, so the readings get very screwy (0 to 256 feet when the depth is about 30 feet). Other than this, the approach has worked fine. If I moved the transducer somewhere else (it's as close to the center of the boat as I could get it), I could probably solve this problem.As far as the wax goes, it's worked fine and gives me the ability to move the transducer. I also have extra wax, if you need it.Now, if you have a good way for mounting the unit itself, please let me know. I'm still looking for good ideas.