This is another example of the excellent work of Phil Gravett AKA Philcraft. It was designed to fit into a small launch type boat hull. To quote Phil - "This engine unit was originally designed to go in a 15" open launch designed by Richard White of ship and boat international, but be able to slip into any suitable hull instantly." I would say that a "suitable hull" could be one a lot smaller than 15". The overall length of the engine is only 5 1/2", and that includes the drive pin on the flywheel! I don't know how many were made originally but there were a couple left over with problems, which Phil left lying around for some time until he fixed them up. He sold the last one to me at a substantial discount - many thanks Phil :-)
The boiler has a butane gas burner. The gas is held in a nice brass tank with what looks like a standard Ronson filler valve, which doubles as a control valve when screwed into place. The burner end is fitted with a ceramic diffuser.
The boiler is a simple vertical type with a single flue. It has wood cladding and a polished brass top plate. The top houses a spherical steam dome and a safety valve identical to those on the Jenny Wren and Lilliput engines. Either the dome or SV can be unscrewed to fill the boiler. The boiler is approx 36mm diam (including the cladding) x 18mm high.
Steam is fed through a stainless steel coil type superheater under the boiler to the engine. The engine consists of a pair of Jenny Wren cylinders mounted in V twin configuration at 90 degrees. The cylinders are only single acting so the engine is not self starting. The pistons are 3mm diameter with a stroke of about 4mm. The crank shaft is terminated with a flywheel 16mm diameter by 13mm thick. This is fitted with a pin to engage with a propeller shaft.