GE "U18B" Locomotives (Baby Boats)

Last revised: December 28, 2022

By: Adam Burns

The U18B was a late model design the company marketed as a secondary, light branch service locomotive.  While GE did sell more than 150 U18Bs, overall it was not extremely successful.

By the 1970s, railroads had lost interest in specialized, non-switcher designs.  To make matters worse, the U18B drew complaints of being under-powered and suffering reliability issues. 

In addition, crews stated the locomotive featured a notoriously rough ride.  It was the Seaboard Coast Line that wound up acquiring the most "Baby Boats," purchasing 105 between 1973-1974.  

The Maine Central picked up 10, the Providence & Worcester a single unit, and Texas Utilities two units. 

Interestingly, Mexico's large Ferrocarriles Nacionales de México (NdeM) also acquired a  large batch of 45 units.  Today, you can still find a handful in operation in the United States, notably at short line Pickens Railway in South Carolina.


31kjnnqoqp9710021931.jpgMaine Central U18B #406, the "Colonel John Allan," leads its northbound freight out of Brunswick Yard with assistance from two GP7s on August 20, 1981. Note the old tell-tales above the first GP7. Randy Kotuby photo.


The U18B was a late addition to the Universal line, beginning production in March, 1973.  It was equipped with GE's standard 4-cycle, 7FDL prime mover that could produce 1,800 horsepower.

The Maine Central was not the largest buyer of the U18B but its fleet was particularly interesting.  As Brian Solomon notes in his book, "GE Locomotives," the railroad acquired the model to replace its old Alco road-switchers (RS2, RS3, and RS11).

Since the locomotives were completed just prior to the nation's Bicentennial (1976) they were listed as part of MEC's "Independence Class."

The units were painted in yellow paint with green pinstriping and featured a massive eagle adorning the nose.  In addition, the railroad named each unit after a notable person or location involved in the Revolutionary War.

The MEC primarily assigned its U18B's to the legendary Mountain Division between Portland, Maine and St. Johnsbury, Vermont.

The remained in use for more than 25 years and some even made it into successor Guilford paint, as illustrated in the above photo.

General Electric offered the U18B with either General Steel Castings' (GSC) swing bolster, drop-side equalizer  (AAR Type B) or GE's own FB2 trucks.

In addition, Seaboard Coast Line had units #325-392 equipped with refurbished Blomberg trucks from  trade-in EMD units.

Data Sheet and Specifications

Entered Production12/1973 (Seaboard Coast Line #250)
Years Produced12/1973 - 10/1976
GE ClassU18B
Engine7FDL (8 cylinder)
Engine BuilderGeneral Electric
Length54' 8"
Height (Top Of Rail To Top Of Cab)14' 14 1/2"
Width10' 3"
Weight220,000 Lbs
Fuel Capacity1,200 Gallons
Air Compressor3CDC (Westinghouse)
Air Brake Schedule26NL (Westinghouse)
Truck TypeSwing Bolster, Drop-Side Equalizer (GSC) or FB2 (GE)
Truck Wheelbase9' 3"
Wheel Size40"
Traction Motors752-E6 (4), GE
Traction GeneratorGT581, GE
Auxiliary GeneratorGY27, GE
MU (Multiple-Unit)Yes
Dynamic BrakesOptional
Gear Ratio74:18
Tractive Effort (Starting)70,000 Lbs
Tractive Effort (Continuous)57,500 Lbs at 10.7 mph
Top Speed70 mph

The SCL was quite fond of the U18B, which replaced its aging fleet of RS2's and RS3's.  They were primarily used in branch and light duty service all across the railroad's network.

In addition, three units #390-392, were assigned to phosphate service in Florida according to Greg McDonnell's book, "U-Boats."

Production Roster

Owner Road Number Serial Number Order Number Completion Date Quantity
Seaboard Coast Line300-30938847-3885628013/1973 - 5/197310
Seaboard Coast Line310-32438857-3887128023/1973 - 5/197315
Seaboard Coast Line325-34339388-39406280711/1973 - 12/197319
Seaboard Coast Line250-26139407-39418280712/197312
Texas Utilities101-10239506-3950728262/19742
Ferrocarriles Nacionales de México (NdeM)9000-901139641-3965228101/1974 - 2/197412
Ferrocarriles Nacionales de México (NdeM)9012-901939653-3966028103/1974 - 4/19747
Ferrocarriles Nacionales de México (NdeM)9020-903739661-3967828107/1974 - 9/197418
Ferrocarriles Nacionales de México (NdeM)9038-904439679-39685281010/19747
Seaboard Coast Line344-39239852-3990029008/1974 - 11/197449
Maine Central400 ("General Henry Knox")4072028245/19751
Maine Central401 ("Hannah Weston")4072128245/19751
Maine Central402 ("General John Stark")4072228245/19751
Maine Central403 ("Peleg Wadsworth")4072328245/19751
Maine Central404 ("Kenneth Roberts")4072428245/19751
Maine Central405 ("Arundel")4072528246/19751
Maine Central406 ("Colonel John Allan")4072628246/19751
Maine Central407 ("Unity")4072728246/19751
Maine Central408 ("Battle of the Bagaduce")4072828246/19751
Maine Central409 ("Ethan Allen")4072928246/19751
Providence & Worcester1810414821408-110/19761


  • Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.
  • McDonnell, Greg. U-boats.  Toronto: Stoddart Publishing, 1994.
  • Marre, Louis A. and Pinkepank, Jerry A. Contemporary Diesel Spotter's Guide, The: A Comprehensive Reference Manual To Locomotives Since 1972.  Milwaukee: Kalmbach Publishing Company, 1989.
  • Solomon, Brian. GE Locomotives: 110 Years Of General Electric Motive Power. St. Paul: MBI Publishing, 2003.

A Maine Central freight, led by U18B #408 (named the "Battle of the Bagaduce"), rolls through Brunswick, Maine during the summer of 1976. Randy Kotuby photo.

Production on the U18B had ended by October, 1976. Apparently, the unsuccessful nature of the model convinced General Electric to scrap any plans to released a follow-up.

This unit would have been known as the B18-7 as part of the company's new "Dash 7" series (offering new electronics among other features).

Today, again, you can find a handful of U18Bs still in operation on short lines although there are none known to be preserved. 

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