Following the manufacturer's directions, light the smoker, cover and allow the heat and smoke to accumulate. In a meat grinder or food processor, grind together the turkey and potatoes until coarsely ground. Transfer to a mixing bowl and add the remaining ingredients, mixing thoroughly. Refrigerate until ready to use. SAUSAGE-CASING Soak the sausage casings for 1 hour in a small bowl with enough water to cover. Rinse the casings thoroughly to remove the excess salt. Running water through the casings will indicate if there are any holes in the casing. Place one of the casings on a sausage horn stuffer, taking care not to tear it, tie a knot in the other end and stuff the casing with the turkey mixture. When stuffed, tie a knot to enclose the open end. Place the sausage on the rack in the smoker and smoke for 2 hours. Turn the sausage and smoke for additional 2 hours.