Look at the Coast Guard statistics on
www.winnfab.com (pages 8-9). According to this "Since 1991, recreational boating fatalities have continued along a downward trend even though the number of registered boats has increased by 15%". Also PWC accidents have had a similar downward trend of incidents since 1996. In NH, accidents are down over 50% since 1999 (page 32). Boats in the 26-40' (the size range where most boats considered "go fast boats" would be) range made up only 10% of accidents, a 1/3 were under 16 feet and over a third were between 16-26 feet. And my final statistic, "Nearly 80% of all reported fatailities occurred on boats where the operator had not received boating safety instruction".
Was this the smartest thing to link to their website proposing a speed limit? I think not. Define excessive speed. Excessive speed could be going too fast in a 16 foot skiff (not coming close to the proposed speed limit but exceeding recommended handling for a boat of its size) with an outboard, or taking a fast turn in a pontoon boat or family cruiser putting its occupants in an unsafe condition.
Education and enforcement of current laws is the key, not a speed limit. I would rather see the MP chasing boating law infractions such as 150' safe passage than sitting in the broads with a radar gun.