Over at The Old Motor, David Greenlees recently posted this mystery engine, unique in so many ways. First, it’s a three-cylinder, air-cooled engine, one that looks rather experimental, judging from its heavy pipe exhaust tubes. Notice also the finned chambers that seem to be separate from the fined cylinders. We can only offer haphazard guesses as to the purpose of those chambers.

Secondly, take note of the belt-driven blower mounted before the engine. David noted that the markings read “B.F.Sturtevant,” and that the Sturtevant blower company, based in the Boston area, had no connection to the Sturtevant automobile built in Boston at about the same time, but its factory was taken over by the builders of the American Napier automobile. At first glance, the blower seems to be forcing air into the cylinders, acting as a supercharger, but instead, it’s acting as a fan, forcing air over the fins to help cool the engine.

Can anybody help David identify this unusual engine? Perhaps the outline of a hood, removed for the picture, can help identify it?