how long does your motor sit? I *try** to use the ethanol treatment on mine when refueling but I also try not to let it set very long. If my 9.9 goes a month without use I believe it will rot away.
The float from Buffalo Point to rush is extremely easy. No difficult stretches. You should not have any trouble with passing rush because just passed rush is clabber shoals.
its tough to say about the gravel. There are lots of deep holes below the gravel mining area below snow. There are quite a few holes on the buffalo that are over 10ft deep and there is zero gravel mining.