We came up from Lake Erie a couple of years ago around the fourth of July, the current was 6 knots in the middle of the river per my GPS speed reading. Ended up towing a sailboat into Lake Huron, they didn't have enough engine to fight the current. I have twins so I was not that concerned about loosing an engine, but if it was a single I would not have been a happy camper until I got out of there. Loose an engine and your best hope would be to get an anchor to catch, river is deep there and that would be hit and miss, then if it did there you are in the river with big freighters which can't be stopped if down bound, I'd call that deadly.
I'm a boater that believes Murphy is alive and well, I'm going to do all I can to stay ahead of him/her.