This little 20HP one-cylinder Diesel engine [1] powers much of third world agriculture. The original design seems to have come from Shanghai Engine Company in 1953, and is still manufactured by multiple companies. It's water-cooled, but non-recirculating; you have to fill the water tank when you fill the fuel tank. No electrical components at all. Starts with a hand crank.

Over 75 years of production of that design. It's the AK-47 of engines.

[1] https://www.alibaba.com/product-detail/High-Quality-Manufact...