Any help would be appreciated. Usual story. Just bought new Raymarine A50D, and no bottom reading over about 400RPM. Tried the tducer at the level of the bottom of the boat and also about 6-8mm below bottom of the boat. It's mounted on the sounder brakcet of the boat, which is a 469 Nomad MP. THe unit I took off was only a cheap Navman, but it didn't get bottom readings either. Just thought with this brand I could get the bottom at speed. ANy suggestions as I said would be much appreciated. Anyone facing the same prioblem or solved the same problem and how?