Rainier-class harbor tug

The ships are built of welded steel plates. They are 90 feet (27 m) long overall, with a beam of 38.25 feet (11.66 m), and a draft of 16 feet (4.9 m).^[7] Their displacement when light is 420 tons.^[4]

They are driven by two Schottel 1012 Z-Drives which have fixed-pitch, four-bladed, ducted propellers. These are powered by two Caterpillar 3512E engines. Each of the engines are rated at 1,810 horsepower (1,349 Kw).^[8] The ships are capable of more than 12 knots when running without a tow. Their engines generate 40 short tons of bollard pull.^[7][9] The Rainier class is the first tug in the Navy to meet the EPA Tier 4 emission standards.^[6] Their fuel tanks have a capacity of 26,000 US gallons (98,000 L).^[10]

Electrical power aboard is supplied by two John Deere 6068AFM85 generators, each capable of producing 154 Kw.^[9]

The tugs have two fire-fighting monitors mounted forward of the wheelhouse, and a pump that will supply them with 2,000 US gallons (7,600 L) per minute.^[9]

The class has a complex fendering system that is capable of pushing both high-sided ships such as aircraft carriers, and the rounded hulls of submarines.

Towing equipment includes an H-bitt on the stern. The tugs have a JonRie 210 series hawser winch on the bow and a JonRie Intertech 421 series capstan on the stern.

The ships have berthing for six people,^[7] but typically operate with a crew of four civilian mariners. There is a small galley, a head with a shower, two single rooms for the captain and chief engineer, and two double rooms.^[11]

The ships are built to American Bureau of Shipping classification standards.^[2]

Navy guidelines for these non-commissioned vessels do not accord them official names. Nonetheless, local authorities have named all of the Rainier-class tugs after mountain peaks in their operating areas.^[12]