Its four boiler 1080 horsepower engine, manufactured by J. Penn & Company of Greenwich,[1] gave it a maximum speed of 11.5 knots measured on August 7, 1874, lower than that of its sister ship the Chanchamayo.

These, the Chanchamayo and the Pilcomayo, were built between 1872 and 1874 by order of the Peruvian government at the Money Wigram shipyards in Blackwall, Great Britain arriving in Callao on January 11, 1875.

[5]: 29 [6] It was ordered out to sea again on June 29, 1879, this time under the command of Captain Carlos Ferreyros, setting sail from Callao and arriving in Arica on July 2 with a shipment of 2,000 rifles for the Bolivian army.

After sending a delegation ashore to assure the local people that he would not bombard the town, he sank the "Matilde" with five cannon shots and destroyed the other boats.

But at 12:20 p.m. he sighted the Chilean ironclad Blanco Encalada, accompanied by the corvette Chacabuco and the transport ship Limarí, coming from Iquique after bombarding es:Pabellón de Pica.

[9] On spotting the Chilean ships, Ferreyros steered close to the coast to escape and then sped away heading north, pursued by the Blanco Encalada for almost 20 hours.

[8]: 486 On November 18, 1879, around 9:00 a.m., the Chilean ironclad Blanco Encalada was in the vicinity of Mollendo when it sighted three columns of smoke to the south that it recognized as the Peruvian corvette Union, the transport Chalaco and the Pilcomayo.

[12]: 457  At this time, Commander Ferreyros opened the valves to flood the engine and the magazine, and ordered flammable material to be poured out so the ship could be set on fire.

The Chilean Admiral Riveros, seeing white flags raised on the boats, gave the order to cease fire and stop the engines so that Lieutenant Roberto Goñi could board the Peruvian ship.

[12]: 457, 518 [10]: 110 The Chileans towed the Pilcomayo into the port of Pisagua, arriving on November 20, where the Peruvian prisoners were taken ashore, before heading to Valparaíso[12]: 480  which they reached on December 4, to the joy of the population who crowded into the streets to pay tribute to the victorious sailors.