Because if the limited construction capacity of the 20 cylinder Mercedes Benz Engines, a class of 16 fast attack boats, the Schnellboot 1939
, was equipped with the less powerful 16 cylinder engines. Because of that, those boats did not archive the high speed of the other German fast attack boats, which made them even more vulnerable than the other boats.
The Schnellboot 1939
had slightly smaller dimensions than the other fast attack boats - which favored them to be relocated to the Mediterranean via the Rhine and Rhone rivers. In 1941 and 1942, all of the remaining boats of this class sent to the Mediterranean this way. There most of them got lost, mainly because of mine hits. Only three of them survived the war and surrendered to allied forces in May 1945.