Islander,
How do you propose people with performance boats deal with the decreased value of boats they purchased prior to a speed limit law? What about marinas with new (and used) inventory that is no longer marketable on the lake? The economic implications are no quite so simplistic.
Also, you mentioned "the big boats are probably 2%", don't know if that's true, but not only big boats are effected. There are plenty of boats in the 21 - 25 foot range that are capable of speeds in the high 60s and 70s. A 24-foot HTM cat with reasonable HP will do 80+. A 20-foot Baja Outlaw with a 7.3L will run in the 60s. An Donzi Sweet 16 will be up there too. Jees, 10 years ago, I had an 18 foot Stingray bowrider that would run in the high 50s.
And least we forget our jet skiing brethren.
Size, al least in this case
, is irrelevant.