I just got my hands on a 1974 Evinrude 9.9 that I have retrofitted the later CDI ignition system onto. I also have the tuned exhaust and different carb from the later model as well.
I got the boat to plane at around 18 knots on a perfectly calm lake with my evinrude 7.5 (roughly 6hp at the prop) and my weight carefully placed. it is flat bottom, so I am guesstimating around 22 knots top speed on calm water, which I think is pretty good for an 8 foot dinghy on a camping trip in the san juans with it this summer where I will be going around 10 miles per day between islands. I have a 6 gallon tank and a 4 gallon tank.
I got the boat to plane at around 18 knots on a perfectly calm lake with my evinrude 7.5 (roughly 6hp at the prop) and my weight carefully placed. it is flat bottom, so I am guesstimating around 22 knots top speed on calm water, which I think is pretty good for an 8 foot dinghy on a camping trip in the san juans with it this summer where I will be going around 10 miles per day between islands. I have a 6 gallon tank and a 4 gallon tank.