In 1781, which James invented the steam engine?

Steam engines already existed. Watt improved the efficiency by use of a condenser.

Somehow if you are observant you can improve and invent things

konablacktraveler, Watt invented a good steam engine; Fulton had improvements incorporated for his steamboat invention.

TestyAlien3443 Robert Fulton is my ancestor. He perfected the steam engine for commercial use. He also gave us the first workable submarine and torpedo.

way back when, we were taught it was a guy named Robert Fulton, but that was when Pluto was still a planet! 😆

So he didn't invent it but improved it