Slice between the bones to cut each rack into two equal portions. Brush ribs with marinade. Transfer ribs to a Dutch oven; drizzle with any remaining marinade. Add enough cold water to cover the ribs. Set the Dutch oven over high heat; bring to a boil. Reduce heat to low. Simmer ribs, partially covered, for 1 hour or until fork tender; remove ribs. Preheat grill to medium. Brush ribs with half of the sauce. Grill ribs, turning and basting frequently with remaining sauce, for 20 minutes or until ribs are very saucy and tender.