The engine room is accessed through a 15x19 inch hatch in the metal casing of the superstructure. The engine is a two cylinder compound made by Mumford dating from around 1920. The cylinder sizes are 6 ½ and 13 inches diameter by 8 inch stroke. It operates at 624 rpm producing 162 HP.
In operation the engine is manned by the engine room stoker who responds to bell signals from the coxswain in the steering position. A simple code is used as follows:
One bell – stop
Two bells – ahead
Three bells – astern
Four bells - ease engine revs
The engine room also houses the main condenser for converting the waste steam back into water for the boiler, circulating pumps for circulating the sea-water for cooling the condenser and two engine driven feed pumps for maintaining the boiler water supply.
The boiler room is a separate compartment. The boiler is a three drum Yarrow type boiler built by Thames Iron Works in 1898. Originally coal fired, the majority of these boilers were converted to oil firing in the 1920’s. 199’s boiler is oil fired using a Laidlaw Drew burner.
It normally takes about 2 hours to reach the operating pressure of 140 to 160 psi from a cold start.
The boiler room also contains a Mumford donkey pump which is capable of bilge pumping from any of the five compartments or pumping feedwater from the tanks or hot-wells into the boiler when necessary. Temperatures in the boiler room and engine room can reach 55oC when steaming but the system is sufficiently stable for the boiler room stoker to spend time at the top of the hatch when on passage for extended periods.