Built in 1976, by McDermott Shipyard Incorporated of Morgan City, Louisiana (hull #219) as the Stalwart for Crowley Marine Services Incorporated of San Francisco, California.
She was the fourteenth Invader class tug constructed by McDermott Shipyards for Crowley Marine Services Incorporated.
In 2018, the tug was "laid up" at Lake Union in Seattle, Washington.
In 2021, the tug was sold to undisclosed interests, where she was renamed as the Stalwart II.
Powered by two, twenty cylinder, EMD 20-645-EG diesel engines. With Falk reduction gears, at a ratio of 4.345:1. Turning two, five bladed, stainless steel, fixed pitch propellers. For a rated 7,200 horsepower.
Her electrical service is provided by two, 90kW, Caterpillar D 3304 generator sets. The tug's capacities are 155,000 gallons of fuel oil, 3,300 gallons of lube oil, and 15,000 gallons of potable water,
The towing equipment consists of a double drum, Markey TDSDW 36C, towing winch. Outfitted with 3,000(ft) of 2.75(in) towing wire on each drum.