Smoking is about cooking to temperature not to time so no one can give you a hard and fast answer. As Mike said, you want to cook to at least 165 degrees internal deep in the thigh. Some people like to cook it a few degrees higher for taste reasons but at 165 it's safe to eat.
Also as Mike said, brine the bird first.
My brine for a whole bird is:
2 gallons water
1 cup kosher salt
3/4 cup brown sugar
1/4 c maple syrup
1/4 c orange juice
freshly groun black pepper
dissolve the spices and herbs in the water, if you heat the water let it cool down completely before putting the freshly washed bird in. Put in a large ziploc or turkey bag and then put it in a pot in case of leaks and sit overnight in the fridge.
Rinse it off well inside and out and smoke it at 300 -325 degrees. I'm guessing about 3/12 - 4 hours but that's an estimate.