I have HDS units and the Air Mar b60 mounted in our 27' Sportcraft. I can mark fish at full throttle. I have, on quite a few occasions, been headed somewhere and stopped and fished marks I found running at full throttle. It just takes a few times of slowing down to get a better look and you'll start learning what good marks look like at high speed. If needed, I can take a picture of where I mounted it. Basically, Port side of the engine, mid way just inside the stringer. I know you can spend a bunch more on transducers, but the b60 has served me well.

Greg