The railroad industry got its first look at Morrison-Knudsen's MK5000C during the Summer of 1994. Driven by a Caterpillar 3612 power-plant, the 71-foot-long newcomer was the first diesel-electric locomotive to reach the 5000-horsepower plateau using only a single V12 engine. Two additional MK5000Cs were finished concurrently to form a 15000-hp demonstrator team. Assigned road numbers 501-503, the trio wore Southern Pacific's Lark grey and Scarlet red with white Espee lettering. A second three-unit demonstrator set was built the following year. Slightly longer at 73-feet, they sported a newly adopted deep blue attire with gold accent striping and numbers 9901 to 9903. The three-some demonstrated initially on the Union Pacific; however, within a year all of the six-axle freight haulers were back at the builder's Boise, Idaho plant undergoing modifications / improvements.

When the MK5000Cs re-surfaced years later, it was under the banner of Motive Power Industries, and they had been re-numbered 9901 to 9906. After a short trial period, Utah Railway purchased all six units in 2001 for coal train service. MPI had already cancelled future production of the 5000-hp model, including three partially constructed units.

The 5000Cs returned to Boise during 2002 and 2003 to eliminate on-going drive-train failures. The Caterpillar engine and Kato traction generator were replaced with a Wabtec V16 645F3B prime mover, along with an AR11 main alternator -- and were dubbed MK50-3s. In 2017, Utah Rwy transferred the MKs to another Genesse & Wyoming subsidiary -- the Kansas-based Kyle Railroad.

As a footnote: MPI also built one SD50M-3 locomotive by mounting a cab and nose section from one of the unfinished MK5000Cs to ex-ATSF SD45B 5501; a 3500-hp EMD 645 engine was also installed. Identified as MPEX 5000, the loco wore Dakota Missouri and Eastern attire and was evaluated by the carrier for use in potential Powder River Basin coal service, which never materialized. It also spent a short stint on the Canadian Pacific.

Notes and Reference sources:

• Extra 2200 South Locomotive Newsletter, Issue 125, December 2003, pages 32-33
• Diesel Era, Volume 12, Issue 5, September/October 2001, page 5
• Don Strack's Utah Rails website
• Wikipedia (Internet)