We recently purchased a 1985 Starcraft 18 foot boat with a 1985 Johnson 90 hp outboard, with the wrong plugs, a cheap plastic prop, full tank of fuel, rough paint job and over 800 lbs of people in it I was able to go 31 mph on its maiden voyage (found out lower unit seal was bad), have replaced the prop and the plugs and the seal and am hoping to get back on the water to see how it does. We don't need to go that fast anyway as its just for fishing. Got what I think was a good deal, trolling motor, 2 fish finders, battery tender for 3 batteries. Just need to fix lines for the live well and install a couple more swivel seats.
I do have a cheap 14 ft aluminum boat with just an electric trolling moter, I had it going over 20 mph or faster 1 time, was fishing down in a mine pond and did not see the storm moving in until the wind hit. 2 foot waves and 40 mph or higher wind, the boat was blown 3/4 of the way up on shore when we finally stopped. At least I was turn the right direction and wasn't swamped.