This V12 air-cooled model boat engine was designed by Martin Ohrendorf of Germany, but the builder of this exact model is unknown. The 60-degree, overhead valve V-12 is machined from billet aluminum (bar stock) with cast iron lined cylinders. It has a bore of 21 mm and stroke is 21 mm, making the total displacement 87 cc. It burns methanol on glow ignition and spins its 24/10 propeller at 4,500 RPM. Each carburetor supplies fuel to four opposed cylinders, and the three carburetors are linked together for smooth operation.
Watch a YouTube video below of a similar engine running. Despite the massive flywheel, it revs fast and sounds good.