I added a depth finder to my old Ski Supreme. The Humminbird with in hull puck tansducer. Overton's product #75681 in black or white. I bought on for my father-in-law last year too for his Ski NotQuite.

They are pretty easy to install. Hardest part is running the wires for the transducer to the back of the boat. I drilled a hole in my battery box on the Ski Supreme, it was closed bow. You should be able to find wires running back that you can use as a guide. If you don't have a blank gauge on your dash the next hardest thing is drilling the hole in your dash/cockpit area.

I would tape the transducer to the bottom of the hull and test to be sure that you get accurate readings before you permanently glue it to the hull. You want it in a place in the hull where there is not much disturbance so you can get accurate readings while running. Typically as close to the center right under or next to the drive shaft in the hull. It is best to test it before you break out the epoxy.

Good Luck.