Try the National Marine Manufacturer's Association's web site.

http://www.nmma.org/facts/

That should give you at least the number of boats registered in each state. As
far as types of boats, only boats with a motor have to be registered (at least
in Massachusetts). Department of Revenue or Tax Collector can give you the
value of boats based on the sales and/or use tax. Finding out the size of the
boats might be the hardest.

"Listen to the live broadcast of 'Nautical Talk Radio' with Captain Lou every
Sunday afternoon from 4 - 5 (Eastern Standard Time) on the web at
www.959watd.com or if you are in Boston or Cape Cod set your radio dial to
95.9FM.