I opened the fuselage hatch today after work and checked the components. The motor ran erratically and didn't rev up. I then unplugged the motor and plugged in a spare motor +plus gearbox +prop for a different plane that I borrowed from a friend.
Guess what? That spare power unit ran perfectly, so the ESC is definitely OK.
Now I'll order the correct power unit for the Corsair and it should be up in the air soon, with a minimum of expense.
Thanks again guys for your input - I learned a lot from this experience.