 In 1924 , four of the ships ' 12 @-@ pounder guns were removed , as were all of their QF 2 @.@ 5 @-@ pounder guns , and a single 40 @-@ caliber 8 cm / 40 3rd Year Type anti @-@ aircraft ( AA ) gun was added . The gun had a maximum elevation of + 75 degrees , and could fire a 3 @-@ inch , 12 @.@ 5 lb ( 5 @.@ 67 kg ) projectile with a muzzle velocity of 2 @,@ 200 ft / s ( 680 m / s ) to a maximum height of 23 @,@ 600 feet ( 7 @,@ 200 m ) . Refitted again in 1930 – 31 , their torpedo tubes were removed as were all of her main deck 6 @-@ inch guns and their casemates plated over ; they now carried only four 12 @-@ pounders . At that time , Iwate also had her boilers replaced by six water @-@ tube boilers , but Izumo was not reboilered until 1935 . The new boilers produced less steam which limited engine power to 7 @,@ 000 ihp ( 5 @,@ 200 kW ) and reduced their top speed to 16 knots ( 30 km / h ; 18 mph ) . 
