I haven't measured the angle but I know it's obviously pretty severe.
Not a very efficient setup at all really:
Losing through the v drive transmission
Losing from the steep angle
Losing from not being able to swing a big enough prop
If I were to do that project over, I would consider losing the v drive, and centrally mounting the engine, and fabricating a tunnel to accomodate a big enough prop.
It's still a very manouverable and comfortable boat. I just think when your only working with 20hps, you may as well get the most out of it.