Mystic in Stonington in Southeastern Region, Connecticut — The American Northeast (New England)
Compound Steam Engine
From Tugboat Socony 5
Horsepower: 850
Cylinders: 2
Bore: 19", 40"
Stroke: 28"
Weight: 40,000 lbs
Length: 8' 9"
Width: 6' 10"
Height: 14'
This large steam engine was built in 1927 by the Staten Island Shipbuilding Company in Staten Island, NY> It turned a 10-foot-diameter propeller on the steel tugboat Socony 5, part of a New York Harbor tugboat fleet owned by Standard Oil Company of New York.
Developed around 1870, the compound two-cylinder engine was a practical power plant for small to medium-size vessels for almost 80 years until outmoded by diesel engines. This example worked with a steam pressure of 160 pounds per square inch. Steam from the boiler first entered the small high-pressure cylinder, driving its piston, and was then exhausted into the large low-pressure cylinder to expand further.
The engine's horsepower of 850 may seem modest by today's standards, but this figure is based on a different horsepower calculation than modern internal-combustion engines. This engine has 10 times the horsepower of the Paine compound engine of the Museum passenger steamboat Sabino.
Erected by Mystic Seaport Museum. (Marker
this page online
Topics. This historical marker is listed in these topic lists: Industry & Commerce • Waterways & Vessels. A significant historical year for this entry is 1927.
Location. 41° 21.572′ N, 71° 57.891′ W. Marker is in Stonington in Southeastern Region, Connecticut. It is in Mystic. It is on Greenmanville Avenue (Connecticut Route 27) north of Isham Street, on the left when traveling north. Touch for map. Marker is at or near this postal address: 41 Greenmanville Avenue, Mystic CT 06355, United States of America. Touch for directions.
Regionally, this marker is on the Connecticut Shoreline, in Greater New London, in Mystic and the Eastern Shore, and in the Thames River Valley. It is also in the American Northeast and in New England. Globally, it is in the North Atlantic Region, North America, the Western Hemisphere, the Western World, and the Anglosphere. Historically, it finds itself in what was once New London County and also one of the original Thirteen Colonies.
Other nearby markers. At least 8 other markers are within walking distance of this marker: A different marker also named Live Oak Log (a few
Other markers no longer nearby. Compound Steam Engine (has been replaced with this marker); Live Oak Log (was a few steps from this marker but has been replaced with another marker now near it); Wichmann Semi-Diesel Engine (was within shouting distance of this marker but has been permanently removed); Lathrop D-90 Diesel Engine (was within shouting distance of this marker but has been permanently removed).
Related marker. Click here for another marker that is related to this marker. This marker has replaced the linked marker which had a slightly different inscription.
Credits. This page was last revised on May 19, 2026. It was originally submitted on June 29, 2023, by Devry Becker Jones of Washington, District of Columbia. This page has been viewed 232 times since then and 24 times this year. Photos: 1, 2. submitted on June 29, 2023, by Devry Becker Jones of Washington, District of Columbia.
