The engine of the MARY A WHALEN is a Model 37 diesel engine manufactured by the Fairbanks-Morse company. Developed in the 1920s, the engine design was tried and true when MARY was built in 1938 (originally christened as the S.T. Kiddoo.) The engine was common to ships of similar age and size to MARY. It was also used in electrical power plants till fairly recently, and perhaps still today.
The brochure provides a consice overview of the parts of the engine and how it works understandable by a layperson, not just a marine engineer.
Some of the diagarams are included here as images. The full copy of the brochure is also linked as a pdf below.
[Thanks to Paul Strubek for scanning the original in his private collection and sharing with us.]