An awesome artifact! I noticed that engines seem to have more power under steam than air. I believe it to due to the density of the propellant.
So under water propellant does the engine have more torque?
Very clever eccentric. After seeing that design I am surprised others haven't pick it up since. Although spring loaded cams do the same. Which begs another question, would spring loaded roller cams give better valve timing than an eccentric?
The patent is interesting, the main issue with water engines is the incompressible nature of water. So his valve design is to reduce the "pound" at the end of the strokes. Some steam engines are designed to intentionally *open* the steam early to provide some cushion at the end of the stroke, very bad for water engines.
Watching the video, the engine isn't that smooth via water, so probably why it didn't catch on? Seems like the valve timing still has pounding issues? I wonder if a pressure relief valve on both ends would have helped? Full size engines sometimes have that. (A 26hp Minneapolis engine does.)
*Corrections as per Gil's reply