For the first part of her life, Hercules was an oceangoing tug. Because of the prevailing northwest winds, sailing ships often employed Hercules and her sisters on journeys north up the coast from San Francisco. For example, in 1916, Hercules towed C.A. Thayer to Port Townsend, Washington. On return trips back down the coast, Hercules often towed log rafts of Pacific Northwest timber, to Southern California mills. At other times, Hercules was employed towing barges to other ports on the West Coast and to Hawaii, and in transporting equipment for the construction of the Panama Canal.
In 1947, she and the tugboat Monarch were given the task of towing the hulk of the battleship Oklahoma to San Francisco Bay to be scrapped. However, 500 miles from Hawaii, they were struck by a powerful storm and the Oklahoma began taking on water and sinking, threatening to drag the two tugs along with her. While the Monarch managed to release her lines, Hercules could not get free until the last moment, narrowly avoiding being dragged into the deep by the Oklahoma.[3] Afterwards, she returned to shuttling car floats and worked in this role until 1957, when she was replaced by the diesel-powered train ferryLas Plumas. Hercules was kept in a stand-by role to the new ferry until 1961.