The hull speed on the Hunter 26 is about 7 knots under power. It only takes a few horsepower to achieve this. If you have wind, waves, or tide to power against, more tourque is better than more horsepower.
The primary limiting factor is the weight of the outboard. The mount is designed to carry no more than a 10 (9.9) HP 4 stroke.
Many prefer long shaft high thrust versions of the 9.9 4 stroke outboards.