Preheat oven to 375. Prepare a 13" x 9" pan with cooking spray; set aside. In a mixing bowl, combine mayonnaise, water, poultry seasoning, sage, marjoram, and salt. Mix well and set aside. In a large skillet, cook onions, celery, and mushrooms until tender. Add to mayonnaise mixture. Fold in stuffing mix and bacon crumbs. Spoon mixture into prepared pan. Bake for 35 minutes, or until lightly browned on top.