Class Petty Officer served as boat captain, with a gunner's mate, an engineman and a seaman on board. Each crewman was cross-trained in each other's jobs in the event one became unable to carry out his duties. Generally, PBRs operated in pairs under the command of a patrol officer who rode on one of the boats. Power The boats were powered by dual Detroit Diesel 6V53N engines with Jacuzzi Brothers pump-jet drives. The boats reached top speeds of . Armament Typical armament configuration included twin M2HB .50 caliber (12.7 mm) machine guns forward in a rotating shielded tub, a single rear M2HB, one or two M60 7.62 mm light machine guns mounted on the port and starboard sides and a Mk 19 grenade launcher. There was also a full complement of M16 Rifles, shotguns, .45 ACP handguns and hand grenades. Some had a "piggyback" arrangement, a .50 cal machine gun on top of an 81mm mortar; others had a bow-mounted Mk16 Mod 4 Colt 20 mm automatic cannon, derived from the AN/M3 version of the Hispano-Suiza HS.404 and also found on the LCMs and PBRs. What the boats possessed in heavy firepower they lacked in armor or shielding. Although the .50 cal machine guns had some ceramic armor shielding and the Coxswain's flat had some quarter-inch thick steel armor plate, the boats were designed to rely on rapid acceleration, maneuverability, and speed to get out of tight situations. U.S. operations From 1966 to 1972 PBRs were operated by the Navy as the principal component of Task Force 116. PBRs were operating with the U.S. Naval Reserve up until 1995 at Mare Island, California, prior to the base's closure due to BRAC action that year. During the Vietnam War, Mare Island was home to the U.S. Navy's Repair Facilities, Mothballing Operations, Submarine Operations, and Riverine Training Operations for both Patrol Craft Inshore (PCF) Swift Boats, PBRs and the River Assault Boats of the Mobile Riverine Force. The training areas for the PBRs and Swift Boats still exist today within the Napa Sonoma Marsh state wildlife area. Sloughs such as Dutchman Slough, China Slough, Napa Slough, Devil's Slough, Suisun marshland and the Napa River all run through the former training area. Since the Navy was busy patrolling the rivers, the U.S. Army had to secure the waters around its military ports. So, it converted the 458th Transportation Company (LARC) into a PBR