There also are many private owners of open boats with small outboards/tiller operated that will rent their boat to you for a day or so. Some CG's even have a list of these rentable boats near them. In most areas away from S.E. Michigan (the Detroit/Flint area) there's really not a problem renting a boat if it's not already rented or reserved of course.
Something to remember is that there are over 11,000 sizeable inland lakes in Michigan not including the vast Great Lakes and more than 38,000 miles of rivers and many are navigable. Hundreds of marinas and over a hundred harbors, so boating, both ownership and renting and boat use is very popular.
What might be more of a problem is finding a full hookup CG on the water that rents boats over 16 feet long tiller operated. Yes there are some but depends on where you are going to want to be.
