Welcome aboard AB,
While it would be helpful to know what type of boat you have, since you specified a "B" or bronze transducer and are talking offshore, I'm going to assume you have an outboard-powered fiberglass hull with a 20-degree deadrise at the transom.
You're on the right track with the Airmar B275LHW
http://www.airmartechnology.com/productdescription.html?id=172 which is a
Bronze,
Low,
High
Wide fairing-block through hull transducer.
Airmar identifies it's CHIRP units by ending the model number in a 5 (Five) so you're getting a 1000-watt Low CHIRP, High CHIRP, wide cone angle unit and don't let anyone talk you out of it!
The only other thing that I would consider is possibly a flush -mount through-hull to minimize a trailer bunk issue.
If the position of the fairing-block 'ducer could be a problem, take a look at the B175HW
http://www.airmartechnology.com/productdescription.html?id=167 While you would be losing Low CHIRP, you would be gaining a bulletproof flush mount which could likely be the last transducer you'll ever buy!