In a 7 1/2-quart ovenproof heavy kettle measuring about 12 inches across combine beans, onion, garlic, bacon, and water and simmer, covered partially, 1 hour. Ladle out and reserve 1/2 cup cooking liquid.
Preheat oven to 300°F.
In a bowl stir together reserved cooking liquid, maple syrup, mustard, and paprika until combined well and stir into bean mixture with enough additional water to just cover beans.
Bake beans, covered, adding water at hourly intervals to keep mixture just covered, 5 hours.