Some have used a wax toilet bowl gasket to figure if the location works. I've used WEST epoxy on a couple boats, mainly because I always have some of their products around. Other epoxies will work. I cleaned the surfaces and coated with un-thickened epoxy. Then mixed in their high strength powder. Mix gentle so you don't get any air bubbles in the mixture. Apply some of the thickened epoxy to both the transducer and the hull and gently install. Some will naturally squeeze out, that's OK. The main thing is to not have any air bubbles, no matter which brand of epoxy you use. Tape in place and let it cure. Transducers don't go bad, or at least not often. The problem is normally the wiring, the head unit, or a connection. If the transducer does go bad, chip and grind in off.....it's bad anyway.
Works like a champ!
Don
Don