24/07/2026
Every American PT boat in World War II carried three Packard 4M-2500 supercharged V12 engines. Three. Each one displacing 2,490 cubic inches (40.8 liters). Each one producing 1,200 HP initially, progressing to 1,500 HP in later wartime versions with higher boost levels and intercooling. Three engines per boat: 4,500 HP total. Driving three propeller shafts through Packard-built Snow-Nabstedt marine transmissions. Top speed: 41 knots (47 mph) in an 80-foot wooden-hulled boat weighing 56 tons fully loaded with torpedoes, machine guns, depth charges, and a crew of seventeen. The Japanese called PT boats "devil boats." The engines that made them devils were Packards.
The 4M-2500 was not a repurposed aircraft engine, despite the persistent myth. Jesse Vincent, Packard's chief engineer (the same man who designed the WWI Liberty V12 and the Packard Twin Six automobile V12), started with a clean sheet in the 1920s for powerboat racing. Gar Wood used Packard V12s in his Miss America speedboats to set world water speed records through the 1930s. When the Navy needed engines for the PT boat program, Vincent's marine racing V12 was the obvious candidate. The production 4M-2500: 60-degree V12. Aluminum block with steel cylinder liners. Bore: 6.04 inches. Stroke: 6.50 inches. 2,490 cubic inches. Four valves per cylinder (48 total). Dual spark plugs per cylinder (24 total). Centrifugal supercharger. Dry-sump lubrication. Holley 1685F aircraft carburetor feeding 100-octane aviation gasoline. Weight: 2,900 pounds. 6.4:1 compression ratio. An overspeed governor cut fuel between 2,500 and 3,000 RPM to prevent the engines from destroying themselves when the boat's hull bounced out of the water in rough seas.
The staggering part is the production volume. Packard built 14,000 marine V12s during the war. Three went into each of the Navy's 768 PT boats. The rest went into Army rescue boats, British motor torpedo boats, Soviet torpedo boats and sub-chasers (535 engines shipped under Lend-Lease), and various allied naval craft. Lieutenant John F. Kennedy commanded PT-109, an Elco 80-footer powered by three Packard 4M-2500s. On the night of August 2, 1943, the Japanese destroyer Amagiri rammed PT-109 in Blackett Strait, cutting the boat in half. The Packard engines went to the bottom. Kennedy and his surviving crew swam to a nearby island. The story of PT-109 made Kennedy a war hero and, seventeen years later, helped make him President of the United States. The engines that powered his boat were Packards.
Today, only one operational PT boat exists: PT-658, a Higgins 78-footer restored by the Save the PT Boat Inc. organization and based in Portland, Oregon. It runs on three Packard 5M-2500 V12s (the final wartime variant). You can hear them run. The sound is unlike anything else in the marine world: three supercharged 2,490-cubic-inch V12s turning simultaneously at idle, each one displacing more than four Chevy 632 big-blocks combined. The Packard 4M-2500. 2,490 cubic inches. Supercharged. Four valves per cylinder. Designed by the same engineer who built V12 luxury cars and WWI aircraft engines. Fourteen thousand built. Three per boat. The engine that powered the devil boats.