RE: Illinois Bowfishing laws..
As Robow said, yes you can bowfish from a boat. Bow does not need to be in a case when the motor is on because you are covered by the fishing code, not the wildlife code. We have copies of the 'bowfishing under power'letter from the state to clarify this. Let me know if you need a copy. (we keep one on the boat just in case)
A caveat about seasons... some bodies of water have a 'bowfishing season'. (some lakes don't allow bowfishing at all) You'll need to check the site specific regulations in the fishing booklet.
A hunting license will not work for bowfishing. You need a fishing license.