Here is what Wikipedia says about the Great Loop:
"The circumnavigation of Eastern North America by water is known as The Great Loop. Also referred to as the Great Circle Route, the trip varies from 5,000 to 7,500 miles (8,000 to 12,100 km) depending on the options used. The boats used range from personal watercraft (jet-skis) to 60-foot (18 m) yachts. Both sailboats and powerboats are used but the most common boats are 34–45-foot (10–14 m) recreational trawlers. The main factors that govern the size of the boat are the limited draft (5 feet (1.5 m)) in some locations on the loop and the height of one bridge (19 feet (5.8 m)) in Chicago."
For powerboats, there is one leg that requires the ability to go 250 miles. That and the height restrictions are the biggest factors for planning purposes.
Many people do this trip on a regular basis and many take years to complete the cycle once.
Thanks for asking about it:
"Its the journey, not the destination"