The SS "Savannah" was too small to carry much fuel, and the engine was intended only for use in calm weather and to get in and out of harbors. Under favorable winds the sails alone were able to provide a speed of at least four knots. The "Savannah" was judged not a commercial success and its engine was removed and it was converted back to a regular sailing ship. By 1848 steamboats built by both United States and British shipbuilders were already in use for mail and passenger service across the Atlantic Ocean—a journey.