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YMS-1-class minesweeper
USS YMS-324 in San Francisco Bay, c. 1945–46
USS YMS-324 in San Francisco Bay, c. 1945–46
Class overview
Name: YMS-1
Builders: 35 yacht builders[1]
Operators:  United States Navy
 Royal Navy
 Royal Canadian Navy
Subclasses: YMS-136, YMS-446
In commission: about March 1942[1] - 13 December 1957[2]
Completed: 481[1]
Cancelled: YMS-482YMS-500
Active: 0
Lost: 32[3]
General characteristics
Type: Minesweeper
Displacement: 270 tons
Length: 136 ft (41 m)
Beam: 24 ft 6 in (7.47 m)
Draft: 8 ft (2.4 m)
Propulsion: 2 × 880 bhp (660 kW) General Motors 8-268A diesel engines
2 shafts
Speed: 15 knots (28 km/h)
Complement: 32
Armament: 1 × 3-inch/50 caliber gun mount
2 × 20 mm guns
2 × depth charge projectors

The YMS-1 class of auxiliary motor minesweepers was established with the laying down of YMS-1 on 4 March 1941. Some were later transferred to the United Kingdom as part of the Second World War Lend-Lease pact between the two nations. One ship, eventually made its way into the Royal Canadian Navy postwar.


The design for the class had a displacement of 270 tonnes. The ships had a length of 136 feet (41 m) a beam of 24 ft 6 in (7.47 m), and a draft of 8 ft (2.4 m). The vessels were capable of 15 knots (28 km/h; 17 mph) , being powered by two 440 shp (330 kW) General Motors (Cleveland) 8-268A, 2-cycle diesel engines which drove two shafts.

The ships had a complement of 32. Their armament comprised one single 3-inch/50 caliber gun mount, two 20 mm anti-aircraft guns and two depth charge projectors.


There were two mostly cosmetic sub-types of the class, sometimes referred to as classes themselves

YMS-135 subclass

This subclass was identical but had only one stack rather than two, and consisted of YMS-135YMS-445, YMS-480, and YMS-481.

YMS-446 subclass

This subclass was also identical but had no stacks, and comprised YMS 446YMS 479.


Eighty vessels of the class were ordered from US yards for transfer under Lend-Lease to the United Kingdom as the BYMS-class minesweeper. Another 53 built for the US Navy (hull numbers 137 to 284) were transferred as further BYMS and another 17 were delivered later.



  • MV Uchuck III, Merchant vessel, USS YMS-123


  1. 1.0 1.1 1.2 Priolo, Gary P. (2006). "Auxiliary Motor Minesweeper (YMS), British Motor Minesweeper (BYMS) Index". NavSource Online. NavSource Naval History. Retrieved 2007-12-20. 
  2. Radigan, Joseph M. (2006). "Ruff (MSC[O] 54), ex-AMS-54, ex-YMS-327". NavSource Online. NavSource Naval History. Retrieved 2007-12-20. 
  3. For both YMS-1 and BYMS classes a total 40 were lost. Of those 40, 32 were YMS-1 class. (See: "YMS class Minesweepers". Retrieved 2007-12-20. )

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