In a 6-quart slow cooker, stir together the first 7 ingredients (through kielbasa). Cover and cook on high 3 hours or until potatoes are nearly tender. Add corn and shrimp; cook 1 hour more or until corn is tender and shrimp are opaque.
Transfer potatoes, sausage, corn, and shrimp to a serving platter. Squeeze lemon over shrimp boil. Serve with melted butter and lemon wedges.