Its not a tilted element so on a v-hull you really need to make a fairing block in order to get it to shoot straight down. I got to thinking that I wanted an aluminum block instead of wood or urethane or some other material but that would take a bunch of machining and I don't have a mill.
I decided to get a chunk of solid round bar as a starting point. In this case it was 3.5" in diameter and 2 inches long. I bored it for the transducer stem on my drill press with a 2" hole saw (I don't have a lathe either) and then cut it at an angle that matched the deadrise on my hull on my bandsaw. The angle was 12°. The piece shown will go inside the hull.
The other piece I welded to the bottom of the boat in an appropriate spot. The inked markings on the hull out ahead of the tube indicates where I am going to build up the fairing ramp to ensure a smooth flow of water over the transducer.
I didn't grab a pic while I was laying in the weld build-up but this is what I ended up with after quite a bit of welding, grinding, filling low spots with JB weld and final sanding.
Here the transducer is liberally swabbed with 4200 and held firmly in the hole with a jackstand and thin wood wedges applying the pressure
Here is the finished install. The fairing looks kind of bloated out in this pic for some reason but its a flat, gradual ramp
Here is the inside piece. I didn't weld it as its under the deck and hard to get to with a torch. Its secured with the 4200 and the big nut at the top of the ducer. I wanted it long like this so to protect the long stem on the ducer.
Anyway, this is how one enthusiast did it, YMMV. I'm a little concerned that I should have also tapered the backside so as to eliminate turbulance but I'll see how it works as-is. If need be I'll put a ducktail on it with JB weld.
Let us know how it works out and performs...