I sincerely think it depends on the particular fish whether or not the sonar sounds repel or not. I've read both ways. I'm thinking in a high trolling traffic area they would get used to it as well as the trolling motor sound.
I've also read a constantly running motor at the slower speeds won't spook fish, at least enough to really tell, but that a motor turning on and off, on and off will readily spook fish.....
Fishing for bass fairly close to the boat, it seemed I had bigger fish striking when the finder was off, just a hunch, but it seemed to be.
Good fishing, Mac