B-4 is the after Motor room.
The equipment located in the aft motor room B-4 is a mirror image of that found in B-2, with the exception that the donkey boilers and evaporator where not duplicated here. However, the degaussing equipment for neutralizing the ship against the effect of magnetic mines and torpedoes was located in this space.
The specific equipment located on the upper level includes the main generation and distribution panel (Switchboard, Forward and After Generator and Distribution, GE, 300kw, 450 volt AC generators, DC generators and DC bus tie, 40kw, 120v), the Emergency Switchboard, the Electrical Degaussing panel, and a Motor Generator Set (Motor-Generator Set, Allis-Chalmers Co. Generator Data: 2 each 8 1/2 KW, 120 VDC; I each 2 KW, 120 VDC. Motor Data: 30 HP, 440 VAC, 1740 RPM.) Also on this level is a High Pressure Compressor and storage tank (Compressor, Air, High Pressure, Worthington Pump Co., 7.5 CFH at 3000 PSI, 6.4 CFH at 3500 PSI, 575 RPM. Motor Data: General Electric Co., 22.5 HP, 600 RPM, 440 VAC) and a Low Pressure Compressor with Storage Tank (Compressor, Low Pressure, Ingersol Rand Co., SN 30R 589, 150 PSI, 750 RPM. Motor Data: General Electric Co., 20 HP, 1750 RPM, 440 VAC)
The specific equipment on the lower level includes the two DC main propulsion generators (Generator, Main Propulsion, Allis-Chambers Co., 1200 KW, 525 VDC, 750 RPM), and the large Electric Drive Motor (Motor, Main Propulsion, Westinghouse Electric Co., Tandem Type, 525 VDC, 2270 Amp, 1500 HP, 600 RPM) that drive the port propeller shaft. There is a small three cylinder Diesel/AC Emergency Generator set (Generator, Emergency Ship's Service, Century Electric Co., 100 KW, 16.7 Amps, 125 KVA, 450 VAC, 60 cycle, 3 phase, 1200 RPM. Diesel Data: General Motors Co., Model 3-268A, 150 HP, 3 cylinder, 2 Cycle.) located here for use when the ship is in port. Also in this space are two fire and bilge pumps (Pump, Fire & Flushing/Fire & Bilge, Ingersoll-Rand Co., Centrifugal, 200 GPM, 100 PSI, 3500 RPM. Motor Data: General Electric Co., 20 HP, 3500 RPM, 440 VAC), Sharples Purifier lube oil/fuel oil.