Chief ES and Deckie Tom.
To elaborate a little, my questions arose from a demonstration last Thursday 28/3 of a museum based two cylinder vertical steam engine, allegedly from a Murray River paddle steamer of the late 19th century, when the restorer repeatedly threw the valve gear (instantly) from 'full ahead to full astern'. I have to admit that the engine looked nothing like a PS engine to me but then I have no knowledge beyond the few Murray River paddlers having steam roller/traction engine machinery.
I always previously thought (still wonder) that this would not be good for the machinery and it was at this point when I asked about cutoff on marine reciprocating that the conversation became confused.
Regards and thanks.
Geoff (YM)