Boats, especially outboards, are much more likely to have issues with low quality gas. It’s another telltale sign that the gas is not the same as off rez gas. Just because you get gas there all the time and your car doesn’t have problems doesn’t mean much. A modern vehicle’s computer can compensate for all kinds of issues. Like I said earlier, keep track of your mileage for a month, then do the same using non-rez gas. If you do it honestly I can almost guarantee the non-rez gas will return better MPG.