tokyoracer,
At first, when you said you could hear the starter spinning but not engaging, I was thinking either you have a bad starter, or no teeth on the flywheel
But, if you can jump start it, that doesn't make sense.
You say the battery is fine...what kind of voltage do you have at the terminals?
Is the smoke coming out the back steam or coolant enriched? Does it have an odor?
Bogatyr