I have a friend at work that is looking to get a 21ft suntracker pontoon boat this spring and wont take my advice at all on getting a larger motor then the 25hp that is standard. He will be using it on the Mississippi River not some small lake i told him that 25hp just seems way too small especially once the boat has people on it. The web site says with the 40hp it tops at 18mph i would think the 25 would not get out of its own way am i way off on this or does he need to take my advice?