John J. Harvey's principal dimensions are 130'x28'x9' with a gross tonnage of 268. The fast, steamboat-like lines of her riveted hull are 5/8" nickel steel plate. Twin screws have three blades with a diameter of 6' and a pitch of 4'4". She is the fastest of FDNY's big boats, capable of speeds approaching 20 knots.
Harvey is FDNY's first internal combustion fireboat, as steamboats didn't have much propulsion power while pumping. Harvey was built with 5 Sterling Viking II 8 cylinder gasoline engines rated at 565 hp at 1150 rpm. All engines drive DC generators rated at 340 kw, with the aft three also equipped with 29 kw generators for auxiliaries and excitation.
The four outboard engines can also drive the fire pumps connected at the opposite end of the engine from the generator.
Built with the redundancy of a naval vessel the electrical plant is completely Westinghouse equipment. A switchboard allows engineers to divide power from any combination of generators to the propulsion motors which develop 1065 hp at 425 rpm. The electric drive for relatively slow shaft speeds combined with the high rpm's required for pumping give an ideal balance for a fireboat's needs. Loss of any one engine does not significantly reduce Harvey's capability in either function.
Harvey is engine-room-operated, commonly known as a "bell boat." Port and Starboard telegraphs are mounted above the Engineer at his station. He stands between the propulsion motor controllers, responding to orders from the Pilot. A third telegraph relays instructions to start or stop fire pumps, as well as indicating the desired pressure.
Four LeCourtenay centrifugal fire pumps are rated at 4000 gallons per minute at 150 psi. Cross connections in the firemain allow them to be set up in series to deliver a total of 8000 gpm at 300 psi. Tests showed the pumps exceeded their rating, pumping over 18,000 gpm (80 tons) which is equal to 20 - or five alarm's worth - of land fire engines.
There are eight Morse "Invincible" deckpipes, or monitors, the largest being rated at 3000 gpm. There are also two manifolds on deck with 24 3 1/2" connections for fire hose. Large reels carried a total of 4500 feet of 3 1/2", 2 1/2", and 1 1/2" fire hose. Nozzle tips, underpier nozzles and distributors, and a wide variety of firefighting tools were also carried aboard.
A 1957 modernization included replacement of the engines with five Fairbanks-Morse 8 cylinder Opposed Piston diesel engines; Model 38F5 1/4" rated at 600 hp.
Part of her significance is that she successfully marked the transition from steam power to a new technology. Her longevity is due to the excellence of materials used in construction, and the care she received from her crews.