It is that one I used to make (much modified from the original plans) as a bit of a commercial enterprise.
You say they are noisy, but I don't think so.
People tend to put too much pressure through them. On live steam, at most 20 psi, preferably 15, they will power a 4 to 5 ft boat. With the correct sized steam prop, about 3" diameter, they just gently nod away giving out plenty of power. It is because it is a long stroke engine, so is designed not to turn very fast.
I think you may have seen these before, the two types of engines I made them into.
This is a nearly 5ft long boat being powered by one of my engines.
He just took out the large Gemini engine, and dropped mine in it's place. It performed a lot better, plus it was much easier to control and more steam efficient.
BTW, a very nice build indeed.