Place rinsed beans in a large pot. Cover the beans with water. Cook over a high flame until it reaches a boil. Turn the heat off, place a lid on the pot, and let the beans soak for an hour. Drain the water from the beans.
Cover the beans with fresh water and simmer for one hour or until tender. Drain the water from the beans.
Place the beans in the slow cooker. Add ketchup, brown sugar, molasses, dry mustard, onion powder, salt, Worcestershire sauce, and water. Stir well.
Check on the beans occasionally and add additional water if necessary.
Cook the beans on low for 8 hours or on high for 6 hours or until beans are tender.
If your slow cooker has a warm setting, you can turn it to warm until you are ready to serve.