I remember those skimmers (called hydroplanes) skipping along the lake in relatively calm waters. They were used mostly by kids and the speed governing was the size of the motor. I believe 10 or 15 hp in the early to mid 60's mostly because of the weight of the motors. They were so much fun back then, but even though the speed was less than 25 mph I'm sure there are several safety features violated (at that age and that low in the water it was really moving). One kid per boat, center steeringwheel, small engines (usually Mercs)
They are still being built, and the horsepower has increased' here is a link where several photos show the assembly process. The skimmer is the bottom right photo.
http://www.glen-l.com/