Transom mount transducer Question.

would like to get some input on mounting a transducer on the transom of our boat. Presently We have a depth finder and data marine unit mounted on the bridge of the boat. Those units are using a thru hull and in hull transducer. Using one of the rod holder mounts, I Was considering placing another fish finder at the stern so I can see whats going on below me without having to go up to the bridge when trolling and drifting. The boat has twin inboards .Should I assume that even at trolling speeds the prop wash would make this transducer useless ?