While I don't personally own a Sportsman, I think I may have had a similar problem with my Renegade. After I washed it for the first time, my machine went into "LIMP HOME" mode. When it does that, it limits the amount of power you can get in an attempt to prevent more damage to the machine. I found out mine was nothing more than loose battery cables. My dealer was able to reset it and its worked like a champ ever since. I wonder if maybe this is the case with your Polaris. Perhaps it has a similar system and sensed something it perceived to be a problem. Next time you start it up, see if you can see anything on the digital display that would indicate problems. I have heard of power cutting out with watery gas too but I can't think how water would get into the fuel system. Good luck with it and keep us posted.
Welcome by the way.:thumbup: