Steve, You said you moved the transducer 3/4 in. Which way and what is the relation to the bottom of the back of the boat.
Decided it would be easier to use pictures to explain. One picture is up close, the other is zoomed out a bit to give you an idea where it is in relation to the motor. The zoomed in picture should give you an idea how deep I set it, which is what you were asking in the second part I think.
The first location I had it was too close to the rib on the right. I thought it was centered, but I was wrong and the interference was from the turbulent water behind the the rib. I moved it to the left about 1/2 or 3/4" so it was as centered as I could get it. Like I said, the first time I did it the edge of the ducer was a little bit behind the rib, that wasn't on purpose... guess I should have been more careful the first time. But thats why I installed a mounting plate, I kind of figured on having to move it around a bit. For what its worth, it was suggested to me to get a transducer mounting plate and I would suggest that to anyone else planning on installing a transducer.
Hope this answers your questions, let me know if you need any help.