The strange case of Canadian National 4824

Six EMD F3s were exported to Canada in May 1948. These were the two ABA sets of order E958 shipped on May 28, 1948 numbered 9000-9005. The booster units were the 9001 and 9004. CN F3A 9005 was wrecked at South Junction, Ontario on May 17, 1958 and was sent to the GMD plant at London, Ontario.

GMD built a general purpose unit for CN on order #A-1714 that used parts of the wrecked F3A. The unit resembled a phase 3 GP9 like all the other GP9s built at that time. The unit was shipped in October 1958. The unit was numbered 4824 to take the roster slot just after the CN's 24 GP7s 4800-4823.

The strange part of this case is how this unit is classified by diesel historians. You can find it listed as a GP7, GP7M, and GP7R. The GMD production records show it as a GP9.

Ed in Kentucky

Horsepower rating of new/rebuilt unit? If it used much of the electrical equipment from the original F3, it might not have gotten the full 1750! And I recall. the choice of the numerical component in designations like GP7M and GP9M that incorporated old components was sometimes surprising....

Wikipedia article on GP9, first paragraph under "Rebuilds" says that there were 31 "GP9M" units built for U.S. railroads with components from older units (and ratings of 1350 or 1500 hp depending on the "organ donor"). So EMD was willing to call a unit a "GP9" if the new-built "locomotive mechanical parts" were of the late 1950s GP9 design, conscientiously adding "M" if the re-used components meant its power was lower than that of a "real" GP9.
My ***guess*** is that something similar occurred here in Canada: the "new" unit was a GP9 in terms of carbody, etc -- it would have been silly to do anything else in 1958 -- but it was a 1500 hp unit. CN would have numbered it into its GP7 series since that's where its operational capacities would have placed it. (It would have been very embarrassing if a freight stalled on a ruling grade because somebody, looking at its number, assumed it would have the tonnage rating of a regular GP9!) And later locomotive historians followed this by calling it (some kind of modified) GP7.
But GMD didn't put the "M" on its names in their records.

(Note, however, the emphatic asterisks around the word "guess" there!)

I have asked the question before. Apparently EMD would use whatever percentage of trade in components that the buyer wanted. A good example is the GN "GP5", which I believe had 1350 hp from the traded in FTs. On the other hand, Boston and Maine also traded in FTs on GP9s. They were "rebuilt" from the FTs, but had stock horsepower. On a FB B&M page they were recently questioning the GP18 fleet. Five were ordered from the 4 BL2s, and a wrecked F&. The sixth was stock, and was a separate order number. The question was whether the first 5 had stock 1800 hp.

I will agree that some wreck rebuilds were real hodge podges of parts. There was a picture of a Southern F, and it looked like a combination of a F3 and FT.