Although rarely encountered these days, in years gone by Stuart Turner's "Sun" was popular with the post-war hydroplane racing movement. It will drive a boat up to 54 inches long and run on either flash or saturated steam - configuration is twin cylinder, single-acting with a stainless steel piston valve gear-driven form the crankshaft. Crankcase is fully enclosed, the engine is fitted with a displacment cylinder lubricator.
Nicely made, it turns over freely.
Length 4 3/4 inches
Flywheel 1 1/4 inch diameter
Bore 3/4 inch
Stroke 3/4 inch