Penta produced outboard motors from 1922. The first famous 2 cylinder motor was the U-2, later named U-21 and U-21S. (Penta also made Volvo car engines from 1927). Penta U-2 was the worlds first two cylinder outboard motor with the cylinders placed in one row above each other. U-2 had alternated ignition of the cylinders which made it not so heavy to start as Archimedes. The rest of the world manufacturers of outboard motors later used this concept. (Year 1959 was the “Volvo Penta Aqamatic” stern drive for inboard engines presented at New York Boat Show).