I was looking at the DX900+, which does depth and speed as well but is electromagnetic. I finally called Airmar and talked to them about it, and the gentleman told me it would not fit in the P17 housing I have. Too bad, it would have been the easiest and best thing.
I finally went with the UST850S-P17-N2, but that only does speed and temperature, so I'm also putting in an in-hull P79 for depth.
I wanted to avoid a paddle wheel if I could.
Best of luck with your project,
West Palm Beach