Yep, built in Dursley england from the 1920's to the 1980's. Not just marine, but light/rural industrial. Typically heavy cast iron, low speed/low horsepower. They have large heavy flywheels, so store a tremendous ammount of energy. As a prime mover for a generator, this large spinning mass is ideal for starting large induction motors. The listeroid I use is a 6/1, 6HP/single cylinder. It is good for 3KW of continous electrical load. But it's large mass will start heavy inductive loads like a generator with a much higher rateing. That is how I can get away with 3KW and still power my well pump.
The engine alone weighs around 750# with 300# of that being in the flywheels. My all-up genset weight is around 1000#. It is started with a hand crank and runs at around 630RPM in my case to get me 60HZ out of the generator. That low RPM Thump, Thump, Thump makes them very pleasant to be around. Way more pleasant than an 1800 or 3600 RPM genset screaming away. With mine running, you can hold a conversation over the top of the engine without yelling. The valve train is almost as noisy as the exhaust is... They are reasonably efficient, and I use just less than .125 gallons per KW/HR of electric load. This slow speed was the main reason for their long service life. They are also extremely easy to work on. With only basic hand tools, I can have the engine striped down to nearly a bare block inside 30 minutes.
Go to Youtube.com and search "listeroid" and you will find a bunch of interesting running videos.