There are a few places I go because I am boatless too. I usually go to Schramms on the North Channel. It is right at the end of Anchor Bay Drive next to Deckers. $50 per boat & you can have it all day. There is also a place on the Clinton River. Roy's Boat Harbor is on the river side about a 1/4 mile west of the DNR Launch. I think they let you have the boat for 8 hours for $40. Then there is Jimmy's on Jefferson North of Crocker. I know that Jimmy unfortunately died last week but I do know that they rent boats. Search the yellow pages on the Internet for Boat Rentals, it will list a few for you.
Hope This Helps,
Hope This Helps,