Prototype Profile: GE U-boats

Prototype Profile: GE U-boats

In 1954, upset that their partner, Alco, decided not to pursue a couple of different locomotive contracts, General Electric released their first solo entry into the diesel-electric locomotive market. A four-unit set (A-B-B-A) of four-axle road units designated UM20s were sent to the Erie Railroad for testing. The units were painted and lettered for the Erie and numbered 750A, 750B, 750C, and 750D, but were wholly owned by GE. Over the next five years, the four-unit set of UM20s served as testbeds for GE’s “Universal” series, which would begin formal production in April 1959 with the U25B. Join us now for a brief look at this month’s prototype profile: GE U-boats.


After they tested on the Erie for five years, Union Pacific bought the four testbeds. Pictured here is UP 620 (ex-Erie 750A). Photographer unknown, from the collection of Chuck Zeiler.

The UM20 units looked like an odd mash-up of the Alco PA/FA series of units (which GE had partnered with Alco on) and the EMD F-series. Though no other UM20s were produced for the North American market, contract builders would continue the series for foreign markets for a few years, including the 43-class series built for the New South Wales Government Railways in Australia.


A contract built 43-class locomotive belonging to the NSW Government Railways. Photographer unknown

For the domestic market, GE began the Universal series with the U25B in 1959. The designation stands for Universal series, 2500 horsepower, four-axles (or “B” designation trucks/bogies). Because each unit in the series started with the letter U, the engines quickly became known among railfans and employees alike as “U-boats”, an allusion to the German designation for submarines during WWII (though there was no connection of any kind between GE and the German submarines).

L&N U25B

An L&N U25B at Etowah, Tennessee in June of 1975. Jay T. Thomson photograph, used with permission.

A total of 478 U25Bs would be built between 1959 and 1966, with the New York Central and Southern Pacific ordering the most (70 and 68 units each, respectively). A six-axle version, the U25C, was produced from 1963 to 1965. A total of 113 U25Cs were built, with Northern Pacific ordering the largest number, at 30 units.


An SCL U25C at Atlanta, Georgia in July 1978. Jay T. Thomson photo, used with permission.

Through 1977, several different units were produced for the domestic market. The U28C began production in 1965, with a four-axle version the next year. The U30B/C and U33B began also began production in 1966. The six-axle U33C didn’t begin production until 1968, a year that also saw the U23B and U23C enter production.

Hi-nose U23B

A Southern Railway high short hood U23B at Alcoa, Tennessee in April 1979. Jay T. Thomson photo, used with permission

In 1969, the U36B began production, with the six-axle version following in two years. Continuing a design that started with the U33B in 1966, the U-boats took on a slightly different visual configuration, with small “wings” at the end of the long hood, a unique aspect to their radiator design. To this day, GEs diesel-electric locomotives still use that design.

Auto Train U36Bs

A trio of Auto Train U36Bs pulling a fast freight as a test run for their passenger service photographed at Savoy, Kentucky in March 1973. Jay T. Thomson photo, used with permission

The final new entry in the Universal series, the U18B, began production in 1973. The small, short, light U18B was designed specifically for branch line duty and it was very successful, with Seaboard Coast Line ordering the most U18s, at 105. In addition to being visually quite short, the U18 also returned to the pre-U33 series long-hood arrangement, with no wings at the radiator section of the long hood.


A former SCL U18B wearing the short-lived blue and gray CSX paint scheme at Corbin, Kentucky in October 1995. Jay T. Thomson photo, used with permission.

The Universal series ended for the domestic market in 1977, with the U23B being the last model still in production. The U-series was replaced in the GE catalog by the very popular Dash 7 series, with the C30-7 beginning production in 1976. The Dash 7 series would stay in production until the mid-1980s.

Santa Fe C30-7

A Santa Fe C30-7 on lease to the CSX at Corbin, Kentucky in November 1995. Jay T. Thomson photo, used with permission.

From 1959 to 1977, GE produced over 3,500 units in the Universal series, including several variants, like the Santa Fe’s U28CG and U30CG, units specifically designed for their passenger trains, the NJDoT/Erie Lackawanna U34CH units for commuter train service, and the giant U50 and U50Cs built for the Union Pacific. U-boats remain popular with railfans and model railroaders to this day, and number of different U-boats have been preserved at museums and tourist railroads around the country.

Santa Fe U30CG

A Santa Fe U30CG leads a passenger train at Iola, Kansas circa 1967. Photo by Mac Owen for a company postcard.

Want to include U-boats on your model railroad? Here’s a few options for you:

N Scale
U25B from Atlas
U25C from Arnold by Hornby
U30C from Kato

HO Scale
U18B from Intermountain
U25B from Bowser
U25C from Rivarossi
U33/U36B from Atlas

O Scale
U23B from Atlas O
U36B from Lionel
U33C from Williams by Bachmann

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Robert Thomson

Robert W. Thomson is a life-long railfan, the son of a former L&N Railroad B&B gang foreman, and an amateur photographer. He was born and raised in southeast Tennessee but now lives in Butte, Montana with his wife, Connie and cat, Charlie. Robert has worked as a park ranger, underground mine tour guide, freelance roleplaying game writer, and ran his own roleplaying game publishing company until selling it in 2012.

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Leave A Reply (4 comments So Far)

  1. Ed Cooper
    2 months ago

    Universal Series production began in early 1956. The 750ABCD were originally two UM12s and two U18Ms. They were upgraded to UM20s before sale to Union Pacific. Domestic production of Universal Series locomotives began in the Summer of 1961. A total of around 400 Universal Series locomotives were sold as export locomotives before the first U25B was sold to a customer. General Electric built six demonstrator U25Bs, which includes the first two #751-752 from 1959, and four from early 1961. And it should be noted that GE was selling both electric locomotives and industrial diesels well before the introduction of the Universal Series in 1956. The last Universal Series locomotive was built in 2005. You have totally ignored the export Universal Series locomotives.

  2. Dan Morgan
    2 months ago

    Edit: This showed up as Dan as the author because Dan forgot to log out before I replied – and I didn’t catch it until moments after.


    Hi Ed,

    Thanks for commenting.

    Every bit of information I have ever found has the UM20s built in September 1954. Also, according to all information I have found, they were only informally known as the UM12s and UM18s but were officially listed as UM20s in the official documentation.

    The hi-nose U25B demonstrators that were later sold to Frisco have build dates of 1/61 and 2/61, however the two XP24 testbeds, which were prototype hi-nose U25Bs were built in 4/59 and 6/59. Most railroad historians count those units as the beginning of production of the U25B line.

    You’ll note that I did touch on one of the export models for NSW Govt. Railways, but that I do point out in the next paragraph that I am primarily writing about the North American domestic market.

    You are correct about GE selling diesel-electrics before this as switchers for the industrial market and for Class I roads as well. I should have specified this was the first solo entry in the road unit market.

    And again, you will note that I do point out that it was the North American domestic market that 1977 was the end of the run for.

  3. Dan Kamikubo
    5 days ago

    U-50s were offered in ho by Athearn recently, U-50s in N-scale were once produced by Con-Cor back in the 70’s.

  4. Robert
    6 hours ago

    Hi Dan,

    I almost listed them, but since they are not currently in production I didn’t. I should have talked about the U50s in the article.

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