If the turkey is completely thawed, I would use 18.5 minutes per pound as a guide. For a 13 pound turkey, this means about 4 hours. I would also monitor with a meat thermometer in the thickest area of the thigh. When the temperature gets to 185 degrees the turkey should be done. If you are stuffing your turkey, I would add another 5 minutes per pound to account for the stuffing. I like stuffed turkey because the stuffing has a really nice smoked flavor when cooked in the Weber. I would keep the vent on the top half open while cooking. Add new charcoal about every 45-60 minutes. You will love a Weber-cooked turkey.