Well look at the label that came with a turkey then subtract about 30 min-45 min if you are using a roaster.
It usually takes me about 4 hours give or take 15 minutes or so. But make sure that it is completely thawed. I usually cook up 20+ lb. turkeys.
If it is still frozen in the middle, scrub out your sink and fill it with cool water, soak the turkey and let the water run into the cavity of the turkey until thawed.