EMD's H engine not a failure??????

It was - at least in North American locomotive service. I believe the number of them in service in the US is about zero, Canada about the same. By contrast, GE's FDL is still available for marine and presumably export loco applications while the GEVO 12 powers the majority of new locomotives built for US service in the last few years.

A story I heard, which I have no idea if it has any truth to it:

EMD was in the horsepower race with CAT/MK and GE for 6000 hp and needed a new engine. I don't know if the reason for going to four cycle was for the higher horsepower or expected emissions issues. EMD is supposed to have given the engineering panel a blank piece of paper and said not to copy or reuse any existing technology - it was to be entirely new. They also used CAD and forgot to include enough metal in the block assembly to dissipate the heat and dampen vibrations. Sounds like the second and existing generations solved that. I can't imagine there were unsolvable electrical or computer problems - but 1000 hp per axle is double what the Dash 2 line was so adhesion would be an issue on poor rail.

GE had stuck with the same Cooper-Bessemer engine design from 1946 going from 100 hp per cylinder to almost 300 using the same cylinder dimensions. Story claims they gave their engineering staff a blank piece of paper and said to use the best proven technology. One mechanic I talked to swears the GEVO borrows from Alco in part. The GE 6000s had the same issues as EMD - teething problems and 6000 hp putting too many eggs in one basket. May be OK on the flat but if you loose a unit on a grade you're going to stall. While the GEVO 16 was unwanted by US railroads, the GEVO 12 has become a standard.

If the real problem with the SD90MAC was electrical - why didn't the 12-265H make any kind of inroads? I have heard many in the industry claim that EMD could meet Tier 4 with the 710, but I don't know what the drawbacks were. I would place some blame on Progress/CAT unable to decide whether to support EMD prime movers or CAT? Remember the 3600 series failures in US loco service with the MK5000C? But I have heard the 3600s do fine in marine service.