The compound engine was manufactured by Mumford dating from 1910. The cylinder sizes are 6 ½ and 13 inches diameter by 8 inch stroke. It operates at 300 rpm producing 162 HP.
When flashed up, the engine room is manned by the engine room Petty Officer Stoker who now responds to engine order bell signals from the coxswain in the steering position although originally orders were passed by a voice tube.
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 pump 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 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 was converted to burn diesel oil fuel.
It normally takes about 2 hours to reach the operating pressure of 180 lbf/in2 from cold.
The boiler room also contains a Mumford donkey pump which is capable of bilge pumping from any of the five compartments, transferring feed water from either reserve feed tank or the hot-well into the boiler as well as pumping sea water when required.
The Hotchkiss Gun
The Hotchkiss 3-pounder gun fitted to Pinnace 199 was built in 1887 and still carries a readable proof plate from 1898. From its markings it is known that it was reproofed in 1945 and fitted on an armed yacht which was sunk later in that year by a German aircraft.
The gun was salvaged from the North Sea by a trawler in its nets in about 1980. It was taken to the Maritime Workshop in Gosport where the gun was overhauled and demilitarised for safety.
When armed with a Hotchkiss gun, pinnaces were often referred to as picket boats as a result of their activities as a picket patrolling the capital ship anchorage. The combination of speed and quick firing ability made the steam picket boat a defence against to the torpedo boat threat of the late 1800s and early 1900s. In addition to the Hotchkiss gun, the picket boat would have carried a number of rifles stowed in the aft cockpit. Steam picket boats were also, on occasions, fitted with a Maxim machine gun or with two torpedoes carried in drop racks on either side of the hull.