My first thought is bad idea.....
The Blackhawk was only built for a couple years. It's basically a Bravo1 upper with a Bravo3 lower. I believe they did not last in the higher horsepower cinfigurations so they were discontinued. But, if I remember correctly........
Blackhawks where designed for high X demension settings on boats with pads & notched hulls. I think Mercury did a bulletin on applications. I haven't searched for it, but it should be available. I'll see if I can find it if you can't.
Blackhawks worked best on boats that naturally carried the nose high. From my deepest recesses of the old brain, that was because they created a lot of stern lift with the dual props. I'm not sure they would work as they were intended on the Deep V of the Cig. Blades or Throttle Up may know more about prop design and what can be done on that issue.
I also recall people having trouble getting the boats on plane because of the required high X, but once they were on plane, midrange acceleration was phenomenal.
One more possible consideration, your idle speed should be around 6 mph or more with only one engine running because of the dual props and around a 27 pitch in your application......
If those things can be figured out, that would be one heck of a cool project.........