Many people ask "Which Nation made the Fastest Battleship?" This question is made more difficult by the fact that not everyone tests their warships in the same fashion. For instance, the British Government prior to WWI and the Italian Government prior to WWII would pay a premium to the builder for every knot above the ship's contract speed. Naturally, the builders took every advantage of this and often forced machinery beyond safe limits. Eventually, this was stopped as some of the tricks included such things as operating the ships without any armament installed.
In contrast, the United States set early standards on how ships were to be tested for speed. From Dr. Friedman's "US Battleships" book:
US Trial Standards
Prior to the Newport Conference (1907), the standard for the US Navy was 2/3 fuel, feed water, ammunition and stores. After the conference, ammunition was increased to full load.
Early in WWII, fuel and stores were also increased to full load. So,
this is important when comparing one nation's ship to another nation's
Apparently, no full power measured mile trials in deep water were ever
made with an Iowa class battleship. During WWII, this was because of the
U-boat threat. After WWII, the US practice was not to perform measured
mile tests. So, I've defined the following information as to how derived.
Also, there's one instance that is documented in both Dr. Friedman's and
Mr. Stilwell's books, which I have indicated with an asterisk - *.
From Mr. Stilwell's "Battleship New Jersey:"
The New Jersey made 32.4 knts. (indicated) during initial trials on 22 July 1943 inside the Delaware Bay. During standardization trials in October 1943 near Rockland, Maine, she made about 30 knts.* over a measured mile, but this was not at full power because the water was too shallow. All trials in 1943 were made in shallow bays, as this made it easier to protect the ship from U-boat attacks. During the infamous "Bull's Run" fiasco, she made 28 knts., sustained.
When reactivated for Korea in March 1951, she made a sustained 32 knts., indicated, during a "full power" run between Puerto Rico and Norfolk, Va. Note: This would be at least partially in "Tropical Waters." After an overhaul in Norfolk, she made 31 knts. on 15 December 1954.
When reactivated for Vietnam, she made 35.2 knts. (indicated) on 27
March 1968 in the Atlantic near Delaware Bay.
From Dr. Friedman's "US Battleships:"
All weights are in "long tons," that is, 2240 lb./ton. = 1018.18 kg.
Standard Displacement: 45,000 Tons
Design Displacement: 53,900 Tons
Design Full Load Displacement: 56,270 Tons
Note: "Design Displacement" is also known as "Trial Displacement." From that, I conclude that it includes 100% of fuel, stores and ammunition, as defined above.
In October 1943*:
55,950 Tons 162,277 SHP 29.3 knts.
In December 1943:
56,928 Tons 221,000 SHP 31.9 knts.
On the basis of the above trial data plus tests with models (both non-propelled and self-propelled), this was equated as follows:
53,900 Tons (Trial Displacement) 212,000 SHP 32.5 knts.
51,209 Tons (Light Ship) 225,000 SHP 34 knts.
During WWII, the Iowa's were considered good for 30.7 knts. under average conditions (foul bottom, moderate sea state).
Since the Iowa's power plant was designed for a 20% overload (254,000 SHP), a fully loaded Iowa could theoretically reach 33.5 knts., or a lightly loaded (51,000 tons) could reach 35.4 knts.
In October 1948, BuShips estimated that adding or subtracting 1,000
tons was equivalent to 0.25 knts. This is important, as it implies that
an Iowa with only half its fuel (which seems to have been the European
trial standard) would be 4500 tons lighter, which should imply a full knot
Based upon the New Jersey's trial data, her fuel consumption was computed
to be equivalent to 20,150 nm. @ 15 knts. and 4,830 nm. @ full power (212,000
SHP), which would be 30+ knts. You can see that doubling the speed quadruples
the fuel consumption.