Thor, the blackhawk is a really short Bravo with dual counter-rotating props. They were usually mounted with an extremely high X dimension to maximize top end speed. The boats that I've seen with this drive ran significantly faster up top (5-10 mph) than they would have with a more normal X, but they were lazy out of the hole and threw a lot of water even at low speeds, not good for skiing. I have never seen anyone running big HP with one, and I'm not sure what sort of upgrade parts are available.
What kinds of boats are you looking at?
-brian