On M-F (only) you can rent a small pontoon for the day (8am-5pm) for $95 - includes a tank of gas.  One of the places will add a fish finder for a few more bucks.   A couple liveries advertise the price, but all will honor the price if you mention the competitors.  Runabouts are cheaper.....$65 I think.
 
Wilhelm also rents pontoons, but I don't remember the cost.
 
If you get 2-3 buddies to go in with you and share piloting duties, it is a very affordable and fun day.
 
NOTE:  Don't waste  your time at Moraine.  Their prices are 2-3x what Pymy liveries ask.