than their predecessors. During sea trials, NUSHIP Fremantle was revealed to be 20 tons over the contracted limit. Main propulsion machinery consisted of two MTU series 538 diesel engines, which supplied to the two propeller shafts. They also had an APU (auxiliary propulsion unit that was fitted in the interest of fuel saving whilst on patrol. (One Dorman 12-cylinder auxiliary propulsion engine) These were later removed as they proved inefficient when compared to the two main engines Exhaust was not expelled through a funnel, like most ships, but through vents below the waterline. The patrol boat could reach a maximum speed of , and had a maximum range of at . The ship's company consisted of 22 personnel. Each patrol boat was armed with a single, bow-mounted Bofors 40 mm L/60 gun as main armament, supplemented by two .50-calibre Browning machineguns and an 81 mm mortar, although the mortar was removed from all ships sometime in the late 1990s. The main weapon was originally to be two 30-mm guns on a twin-mount, but the reconditioned Bofors were selected to keep costs down; provision was made to install an updated weapon later in the class' service life, but this did not eventuate. Early on in the construction program, it was realised that the two main patrol boat bases, in Cairns, Queensland and in Darwin, Northern Territory, were not capable of supporting ships of this size on a permanent basis. This resulted in a $10 million infrastructure upgrade for the two bases, which was completed in 1981 and 1982, respectively. This included modern maintenance, logistic, and administrative facilities at both bases, and the installation of a synchro-lift at Coonawarra. Construction of Fremantle began in October 1977. It was launched on 16 February 1979, and commissioned on 17 March 1980. During sea trials, Fremantle received distinction for locating and rescuing a British sailor thrown from a commercial trawler following its collision with an oil tender. Construction of the first Australian-built vessel, , began in September 1978, with Warrnambool launched on 25 October 1980 and commissioned on 14 March 1981. The final ship of the class, , was commissioned on 15 December 1984. The Australian-built vessels were built through an assembly-line method. Hulls were built upside-down from the keel to the second-uppermost deck, then rolled over and built to the top of the hull. After this, the superstructure, which had been fabricated at the