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Gem Marine Steam Unit


This is a simple small marine engine.

The horizontal boiler is approx 2" diameter x 2 3/4" long and is made of copper. It is totally enclosed in a brass outer wrapper, which has holes for the burner and safety valve; and to allow the burner gasses to escape. The burner is a meths wick type using a 1" wide flat wick. The only boiler fitting is a safety valve.

Steam is fed directly to the port face incorporated in the cast mazac(?) frame. The single acting oscillating cylinder is 9/32" bore x 1/2" stroke. The cylinder is in two parts; the barrel being brass and the top end, including the port hole, is mazac. There is a brass cup mounted on top of the frame with a small hole to drip oil onto the port face.

The piston is connected to a cast mazac crank, with nominal balancing, and a 3/4" diameter cast mazac flywheel. The flywheel carries a pair of pins for driving a propeller shaft.

As acquired, the safety valve and the burner were in need of repair. I have repaired the burner and fitted a Mamod S/V for the time being. Paintwork appears to be original and is in reasonable condition for it's age.

Make Gem
Model Marine Steam Unit
Made c1946-47
Description Marine engine
Cylinders 1
Cylinder Type single acting
Bore mm 7.25
Stroke mm 12
Valve Type Oscillating cylinder
Boiler Type Horizontal
Boiler Diam mm 51
Boiler length/height mm 70
Fuel Meths
Mechanical Condition Good
Cosmetic Condition Fair
Paintwork Original
Packaging Cardboard box
Purchased 31 March 2019
Purchase cost 155
Additional spend