The aft location should be fine unless there is something else forward of your chosen spot (hull strakes for example).
The objective is to have undisturbed water flowing over the face of the transducer -- no air bubbles, turbulence, etc, that would change the acoustic properties and mess up the signal transmission.
The proximity to the spinning shaft should not be a problem, though remember that the stuffing box area where the shaft comes through the hull will disturb the water a bit so if you can be a tiny bit forward of that it would be good.
My in-hull transducer is sitting between two 330 hp Diesels less than a foot away on each side and works perfectly despite the rather large amount of spinning metal and a bunch of electronic engine controls. |