Good question Hoss68.
When I go fishing I'm generally on my own so I don't turn the engine off, simply fire her into neutral and drift.
There is a spot I go to where I have brought crew along also. However it is an inlet with cliff faces each side and rocks sitting in deep water, so no turning off the engine there either
Always did wonder about it though. Last few times at this place, fish finder was spotting the fish, but no bites. I wondered if the engine sound was keeping them away. No good answer for that maybe I need to get the anchor out and try with her shut down .....
Welcome to the group hoss68.