Craftsman Tractor Won't keep running

Craftsman DGS6500 - 944.607092 Kohler Courage 26 HP Engine I use the tractor with a snowblower attachment and this season it hasn't been running well at all. When I first start it, it runs fine for about 20 minutes when it starts to act like its lacking fuel, engine power drops noticeably before the engine eventually dies. Chocking can usually keep it running for about 30 sec. If I let it sit for about 10 minutes I can run it for a minute or so before the same thing happens. I'm not terribly mechanically inclined but I've checked the fuel filter and there is plenty of fuel flow from there.