Larry;
If a thru hull transducer, there is only one place on that boat which is below the rear berth to the starboard side of the bilge pump but a little aft for the flattest area where to install. Make sure that you use no larger than a two inch hole saw and remove all paint on the outside of the hull where the outside of the flange of the transducer comes in contact with the hull. Suggest that you lightly sand and liberally use 5200 when installing. Leave that transducer alone for a week to let cure and dry.
The other is to install it inside and you will have to sand the surface smooth cleaning off with acetone or alchohol, Never thought plummers putty would work but Kermkit made me a believer of that. There are other modes of attachement though. '
as for a puck style attached to the end of the boat, I was never really a fan of that style. you still have to cut a hole for the wire to run thru anyway you look at it.
It is good to ask questions but are you sure that you are not taking on too much at one time?