Preheat oven to 350 degrees, with roasting rack in lowest position. Stuff and prepare turkey for roasting.
Set roasting rack in a large roasting pan. Place turkey on rack; rub all sides with butter, and season generously with salt and pepper. Pour 3 cups water into roasting pan. Loosely cover turkey with aluminum foil (unbuttered). Roast 1 hour, then baste every 30 minutes with pan liquids until an instant-read thermometer inserted into thickest part of thigh (avoiding bone) registers 125 degrees, 2 to 3 hours.
Remove foil; raise oven heat to 400 degrees. Continue roasting, brushing 3 to 4 times with maple syrup, until thigh reaches 170 degrees, 45 to 60 minutes more (temperature will rise about 10 degrees as turkey rests after roasting).
If bird browns too quickly, loosely cover with buttered foil; add more water if pan becomes dry. Transfer turkey to a serving platter, cover loosely with buttered foil, and let rest at least 30 minutes before carving so juices are reabsorbed. Reserve pan for making gravy.