The Medium Tank M4A2E1 was a version of the Sherman tank that was powered by a General Motors engine developed from a marine diesel engine.
The General Motors 16-184A was a vertical four bank 16 cylinder marine diesel engine, produced for use in US Navy 110ft submarine chasers. The V8-184 was developed by GM as a private project, and was basically half of the 16-184A. It was a water cooled V-8 engine that provided 600 gross HP at 1,800rpm.
In September 1943 the Ordnance Committee decided to order the V8-184 and install it in a medium tank. Two engines had been delivered by February 1944, and one was installed in an M4A3. This required another 11in to be added to the back of the tank, and the type had a sloped rear plate.
The prototype underwent tests at the Aberdeen Proving Ground between May 1944 and March 1945. It gained the M4A2E1 designation on 20 July 1944, during these tests.
The new engine performed well. It had a high power to weight ratio, and gave the M4A2E1 much better performance than the standard Sherman. During the tests the tank drove 2,914 miles without any serious problems. At the end of the trials it was suggested that more research should be carried out into the use of two stroke diesel engines in tanks, while the 16-184A marine engine was considered for use in heavy tanks.