Riggs Patent Reversing Gear

[Johnlanark]

I was browsing an old book "Drawing for Machinists and Engineers" and came across this idea which I have not seen before.
If the crank of a single cylinder engine stops at dead centre, no motion can take place until it moves sideways a little. Cam F and roller G are carried on plunger H, which has steam pressing underneath it, and so moves the crank.

I wonder whether this could have a use in a boat? Could the valve be left open or would this stop the engine from rotating?
John

[barts]

For small engines, I just give it a spin w/ my hand . If I had a boat where the
engine was too big to jog or where I needed to be at the wheel rather than
next to the engine, I'd fit a permanent magnet motor so it would function as
either a generator or a "starter" motor.

- Bart