Randy:

If the voltage sags to 10V, then the battery is dead.
That requires either a battery failure or a failure in the
charging circuit that is not noticed for a couple of hours.

You reported that the voltage was 14.7 at least part of
the time when unloaded. That implies at least partial
function from the voltage regulator and alternator.
It could mean that one or more of the six rectifiers
is fried.

I would recommend separately testing the alternator
and the battery. An auto parts store or auto alternator
specialty shop should be able to test both.

-bob