 During refits in 1923 – 25 , the fore funnel was rebuilt in a serpentine shape in an unsuccessful effort to prevent smoke interference with the bridge and fire @-@ control systems . The rebuilt fore funnel was eliminated during the ships ' 1930s reconstructions when their boilers were replaced by 10 oil @-@ fired Kampon boilers , which had a working pressure of 313 psi ( 2 @,@ 158 kPa ; 22 kgf / cm2 ) and temperature of 300 ° C ( 572 ° F ) . The turbines were also replaced by lighter , more modern , units and their propellers were replaced by larger 4 @.@ 3 @-@ meter ( 14 ft 1 in ) ones . When the ships conducted their post @-@ reconstruction trials , they reached a speed of 24 @.@ 98 knots ( 46 @.@ 26 km / h ; 28 @.@ 75 mph ) with 82 @,@ 300 shp ( 61 @,@ 400 kW ) . Additional fuel oil was stored in the bottoms of the newly added torpedo bulges , which increased their capacity to 5 @,@ 560 long tons ( 5 @,@ 650 t ) and thus their range to 8 @,@ 560 nmi ( 15 @,@ 850 km ; 9 @,@ 850 mi ) at 16 knots . 
