My old Starcraft Utility weighed 450# (deluxe model with floor) and it would reach 25 mph with a 25 HP 2-stroke and 2 people.
Propped right, your 20 will "perform" OK, but not at your desired speed. Go with a 30.
Jim, its apples and oranges if you are talking about today's 25 and the rude in your avatar. Back when I was a kid, that engine would run a 16' plywood skiff with windshield and side mounted controls, 2 fishermen, 2 ea. 6 gallon tanks of gas, a livewell full of shrimp and tackle, fast enough to have to cut the throttle in the chop in Galveston (Tx.) Bay.
