I am wondering if maybe it was just an overheating problem.
-- you may wish to pull the shroud off and gunk down the engine and cylinders - making sure the engine is thourougly clear of excess dust and blockages.

engine works around an hour mowing grass and is well warmed up,it starts sputtering and missing and lacking power...

--- Pull and examine the plug(s), if their dark/black your probably running too rich. You will need to find and adjust your air fuel mixture.

If this were to be the problem - adjust your air/fuel mix a quarter turn at a time and then examine your plugs on each mowing - and adjust accordingly until you get a light brownish appearance on your inner insulator of the plug. After a few mowing's you should be close to zeroing in on the ideal air fuel setting.

the only other things I can think of (at this time) is water in the fuel bowl of the carb. This would cause the engine to spit and sputter .

good luck

How do you adjust the air/fuel mixture on that engine? I see where you adjust the idle richness and idle speed, but no high speed adjustment.

IF it runs well for an hour, I don't see how it could be a carb adjustment!

If you think it's heat related, remove the COOLING shroud and clean the debris from the COOLING FINS.

Have you checked the gas cap vent? Maybe it's restricted enough so that after an hour, enough vacuum has built up ithe fuel tank to prevent adequate fuel flow?

Have you actually checked the spark when the problem occurs?
You might check the spark with the engine cold first, so you can compare the 2.

This link lists the engine as a FC540V
http://www.smallenginewarehouse.com/RepowerItems.asp?Brand=John%20Deere&Model=265

My mistake, it is a model FC540V. I have removed the cooling shroud and it is perfectly clean. The groove in the tank filler tube shows that the vent is working fine. When it is running badly, the spark plug is a light gray color, the same as when it is running right. Although the coil was new in January, this does not mean that it is OK now. This engine ran perfectly until all at once when it started sputtering and missing which means something failed at this time. I just hate to spend another 50+ dollars on another coil only to find that it is not that. I have heard that a Briggs and Stratton coil will work on this engine. It sure looks alot like one. I wish I knew what model B&S engine it would be used on. I read about this on another message board a couple years ago. Thanks for all the info. Let me know if you can find anything more. sfhill

If the spark is not bright blue when this happens, you could have another bad ignitor.

I found the problem and have got it fixed. Remembering that the pto clutch was noisy before, I checked the switch and found that it would not click while snapping it off and on. Also I could not turn the pto pulley by hand which I used to be able to do. I removed the clutch and the top bearing was burned blue from heat and it was locked up. I turned the switch on and it immediately started up and ran perfectly. What had happened was the clutch totally seized up and stopped the engine from turning while the throttle was open while mowing which caused the explosion sound and black smoke from the muffler when everything stopped working. This new Warner clutch cost me $137.80 at my local John Deere dealer and I was very satisfied. I have it all together and ready to mow. Thanks to everyone who tried to help. One just never knows whats wrong until you get to working on the problem. sfhill