Within the past year one of the model magazines (I think Model Airplane News but not sure) had an article where they deliberately added water to fuel in small percentages at a time and found that even with more than 5% water, the engines run fine. Also, many years back--about 30--a fellow modeler did the same test with the same results, in fact with a small amount of water, the RPM went up. In all my years of flying, now well into the 50th, I have never found moisture in the fuel to be a problem.