Built in 1973, by McDermott Shipyard of Morgan City, Louisiana (hull #186) as the tug Ocean Wave for the L and L Marine Service Incorporated of St. Louis, Missouri. A subsidiary of the Apex Oil Company of St. Louis, Missouri.
In 1981, the tug was transferred to the Apex Oil Company of St. Louis, Missouri. Where she was renamed as the Inca.
In 1988, the tug was acquired by the Morania Oil Tanker Corporation of Staten Island, New York. Where she was renamed as the Morania No. 4.
In 2000, the Morania Oil Tanker Corporation merged with Penn Maritime Incorporated of Stamford, Connecticut. Where the tug was renamed as the Penn No. 4.
In 2012, Penn Maritime Incorporated was acquired by the Kirby Corporation of Channelview, Texas. Where the tug retained her name.
In 2013, the tug was outfitted with a JAK-400 coupler system at Feeney's Enterprises in Kingston, New York.
In 2016, she was phased out of active service, And was "laid up" at the Kirby Corporation's yard in Staten Island, New York.
In 2018, the tug was acquired by Curtin Maritime Incorporated of Long Beach, California. Where she retained her name. And the tug was "laid up" at Therodore, Alabama.
Powered by two, twelve cylinder, EMD 12-645-E5 diesel engines. Turning two, cast steel, fixed pitch propellers. She is a twin screw tug, rated at 4,300 horsepower.
Her electrical service is provided by two, 75kW generator sets. With a third, auxiliary 75kW generator set. The tug's capacities are 120,727 gallons of fuel.