To mount my fishfinders two transducers to my twin-engine catamaran, I bought a couple of salt water trolling-motor transom mounts. A local welder permanently attached each transducer bracket to the bottom of a tube that fits in the motor mount. I then clamped the motor mounts to the transom, just outboard of my engines. These mounts are very sturdy, look good and didnt require me to drill any holes in my hull. And they allow me to swing the transducers up out of the water easily, adjust their depth, or even rotate them.
Ronald LaCroix, Anaheim, California