I did a lot of research on sonar transducer combos and it looks like the Simrad NSS evo2 is working very well with the Airmar B175HW. It's a 150-250 kHz chirp transducer with a 25 degree beam width and the screenshots I've seen on thehulltruth.com are incredible.. The B175 is a thruhull model that requires a 4" hole cut in the hull which I'm not willing to do. However, the B285HW has the same internal elements as the B175HW and has the same form factor as my existing B258. I don't need to cut any more hull, just remove current transducer and install new one with sealant. I won't use the high speed fairing but I don't think I need it as I can track bottom at cruise with current setup. Starting install this weekend.