In September 1876, "Mesudiye" became the flagship of the Ottoman Black Sea Squadron, though she did not see action in the Russo-Turkish War that broke out in April 1877. After the Ottoman defeat, the fleet was laid up at the Golden Horn and left largely unattended for the following twenty years. The annual summer cruises to the Bosporus ended. By the mid-1880s, the Ottoman ironclad fleet was in poor condition, and "Mesudiye" was unable to go to sea. Her engines were unusable, having seized up from rust, and her hull was badly fouled. The British naval attache to the Ottoman Empire at the time estimated that the Imperial Arsenal would take six months to get just five of the ironclads ready to go to sea. Throughout this period, the ship's crew was limited to about one-third the normal figure. During a period of tension with Greece in 1886, the fleet was brought to full crews and the ships were prepared to go to sea, but none actually left the Golden Horn, and they were quickly laid up again. By that time, "Mesudiye" was probably capable of little more than , but her poorly-trained crew was likely unable to keep that pace for an extended period of time.