Small Engines (Lawn Mowers, etc.): Lawn Mower dies after 10 minutes, champion spark plugs, spark tester

Question
I have a 6.5 HP Craftsman walk behind mulching mower (model # 917.387480).  After 10 minutes of mowing the engine begins to sputter (puffing sound through the muffler) and then dies. It then needs 10 minutes to cool down before I can start it back up again.  I will have about 5 or 10 minutes before the engine dies again.  I have replaced the spark plug, air filter, and there is fresh gas in the tank.  What could be causing the problem?

Answer
It could be a bad coil.  Do you have an inline spark tester?

What brand of spark plug are you using?  If it is a Champion or Sears plug then try another plug.  We frequently have this happen with Champion spark plugs...even brand new ones.

Let  me know.
Eric