Motor Launch
19 September 1943
Dimensions & Displacement
Length 42 feet
Beam 12 feet
Draught 8 feet 3 inches
Speed 8.5 knots
Guns 1 x .303 inch Vickers machine gun
Other Armament 2 x Mk VII depth charge, 10 x Midget depth charge

With much of the Royal Australian Navy fleet deployed to foreign waters in the early years of World War II, the defence of Australia’s coastlines became a primary concern for the Naval Board. The Naval Auxiliary Patrol (NAP) was a war-raised unit approved on 25 June 1941, charged with patrolling and safeguarding Australia's inner harbours, ports, rivers and estuaries against enemy sabotage or attack. The NAP fleet was comprised primarily of former pleasure craft, offered freely by their owners.

In May 1942, the NAP was transferred to the Royal Australian Naval Volunteer Reserve (RANVR) and was thereafter known as the RANVR NAP. By October 1942 the total strength of the NAP had increased to over 3000 mobilised and unmobilised reserves. This was to remain the case until early 1944 when it was considered that the danger of enemy attack was remote enough to reduce the strength of the NAP to a minimum.

Marynong was a 42 foot Motor Launch that served as a Naval Auxiliary Patrol vessel. The boat was requisitioned for naval service on 7 January 1943, before being commissioned into the RAN on 19 September 1943. HMAS Marynong was purchased by the Australian Government on 19 January 1943. HMAS Marynong was decommissioned and later sold on 27 October 1945.

HMAS Marynong first appeared in the April 1944 edition of the Navy List:
HMAS Marynong first appeared in the April 1944 edition of the Navy List: