She was powered by 2 triple expansion reciprocating steam engines, driving two shafts, which developed a total of 7,403 indicated horsepower (5,520 kW) and gave a maximum design speed of 27 knots (50 km/h; 31 mph).

Alagoas carried a maximum of 140 long tons (140 t) of coal that gave her a range of approximately 3,700 nautical miles (6,900 km; 4,300 mi) at 14 knots (26 km/h; 16 mph).

In addition, four 47 mm (3pdr) cannons in single mounts were deployed at the time of launching.

The official full speed trial for Alagoas took place on November 26, 1909 on the Skelmorlie deep-water measured mile at the mouth of the Clyde.

During a continuous three hour run with a 100 ton load, the ship exceeded her contract speed of 27 knots.