I'm using an 8hp 2 stroke bought in the early 90s. I've never felt that it was less than adequate for the job. And the boat was originally designed for using a 6 hp 2 stroke.
If you're in the US it's getting more difficult to find new 2 strokes. From postings on various sites it seemed a lot of folks favored the 9.9 hp motor. But the issue was always how the head fit into the notch and the limited tilt due to the larger size of newer motors.