I don't know if this is true, but if you were in a dark area and the mower had run more than a few minutes, it isn't unusual for the exhaust manifolds to have a red glow to them. they operate around 700 degrees at full throttle.
If the mower will run with the jumper cables, get us a volt reading with the engine running. Should be around 13.5 at full throttle. I suspect you are below 12. So it that is true that you will need to disconnect the wires going to the voltage regulator, It will be the small box on the opposite side of the engine at the starter. Connect each lead to one of the wires in the double connector, and set the meter to read AC. Should be 28v AC or higher. If that is true then replace the voltage regulator. If the AC voltage is below 28 v then you will need to replace the stator under the flywheel.