I think the only issue with these is when the transducer is mounted either too far forward or two far back.
Too far forward and you might get churned up water hitting it which could lead to poor readings. Too far back and you get cavitation off of the prop which would lead to air bubbles doing the same thing.
I've always been told that some where near the raw water pick up(IE not in front of it) and before the strut is a good place. You're looking to get the least amount of disturbed water across the point of the transducer.