If your boat is registered in your home state (I am assume it's Indiana) then you can fish that boat anywhere, in any state. You will need to comply with fishing license requirements for the non-resident state though. If you are fishing a river that forms a communal border between the states it is likely there is a reciprocal agreement between the states to allow you to fish these waters, however you may possibly not be able to fish the backwaters on the non-resident side without possession of that state's license. A quick check of your state's game laws should clear up your questions.
Alright, thanks. I'll look into that. Wasn't sure but everyone here cleared it up for me.Paul,
If your boat is registered in your State of residence it should be fine in Illinois. The boating regulations may differ from state to state so pay attention to them but other than that it should be fine. Also one other thing is state lakes, some of them require purchasing a permit sticker before you can fish them so make sure you check this out too. rspd507