Is the existing Airmar an IN hull or Thru Hull? Do you year 330 have "transducer flats", flat areas for mounting bronze thru hulls without needing a fairing block?
Your hull is 19.5 degree at the transom. Higher as you go forward. Edit: the newest 330 is 20 deg at the transom. I thought they were less. They might vary by year but not by much. They are all closer to 20 than 12.
If you have a flat and its wide enough, you can mount a 0 deg B175 there.
Otherwize, if you mount on the slope, you need a 20 degree B175.
The B175 is a single chanel CHIRP. It comes in Low, medium, high, or High&wide
If you have transducer flats, and your sonar is CHIRP, Dual channel, then IMO you should use a B275LHW