Look for a copy of River Horse
by William Least Heat-Moon. He had the same notion you have now, so he obtained a 22' motorized vessel and, accompanied by various companions along the way, traversed some 5000 miles from New York
Harbor to Astoria, Oregon
Don't kid yourself, though. The journey is impossible without portaging often, thanks to the seemingly endless efforts of the Army Corps of Engineers to put a dam on every wild river in the west.
Try here: Amazon.com: River-Horse: A Voyage Across America (0046442636261): William Least Heat-Moon: Books