I really appreciate the info I've got here and just wanted to post this for anyone having a similar problem.

Tractor: Craftsman (917.256580)

Engine: Kohler Command 15.5 HP

Symptoms: Tractor was running great. One day while mowing, the engine started surging for about a minute and then shut off (like it ran out of gas). If fact that's what I thought happened. Grabbed the gas tank and went to fill it however there was plenty of gas in the tank. Couldn't figure out what was wrong so I put the mower away. Tried it the next day, it ran great for about 15 minutes and then did the exact same thing.

Solution: Bad fuel pump.

Price to replace: 35$

The fuel pump for this model tractor is located on the opposite side of the air intake. The fuel hose comes from the tank (under the seat) to the fuel filter, and then from the filter straight to the bottom of the fuel pump. To test if the pump is bad, you can remove the hose from the top of the pump and turn the engine over (for about 5 seconds). When I did this with my bad pump absolutely nothing came out. After replacing with the new pump gas came shooting out of there like a water fountain.

Replacing the pump is easy. Disconnect the input fuel line (on the bottom). Becareful here gas will come out when you pull it off. Disconnect the fuel output line (on the top). There are two screws which hold the fuel pump onto the engine. Remove these and the pump will come off. You may have to pull it as there is a gasket between the pump and the engine which may cause some sticking. Install the new pump, reattach lines and you should be good to go.

Best of luck,

Dave