If your boat has a solid fiberglass hull, installing the transducer should take about 1 minute. You can use a 'puck' type transducer instead of a through hull. You don't need to epoxy the transducer or mount it in a tube filled with oil. All you need is some toilet bowl wax (about $1.00 from Home Depot, etc.). Press a wad of wax onto the hull where you want to place the transducer, then press the transducer into the wax.
I did this about a year ago. I originally planned on using the wax to find a good location, and then epoxying it in. However, since it has worked great, I have no reason to glue it down.
I used a smear of 4200 in front of the keel root, aimed about 8-10 degrees forward. That gives me the view directly beneath my bow, and the depth is "my keel plus six inches for waterline variables"!