I am here because i know there are a lot of knowledgeable people here. I am a very curious person and have a fascination with steam. This is purely from a theoretical standpoint, and to better understand the effects of deterioration on locomotives. I'm sure many of you know of the CPR 694 in Lake Superior.
https://www.youtube.com/watch?v=nTfWHoqZfGQ
https://www.youtube.com/watch?v=cXk-oAqgbtw

This question rarely gets asked because a lot of old heads tend to scoff, but i can't help but wonder, if in theory, from a purely mechanical standpoint, if this locomotive is capable of being restored to operation? It's over 200 feet down, in fresh water, it had a rough ride down of course, but looking at the video, it appears the frame of the engine and the driving wheels, they look to be pretty solid, and in some areas i can even see black paint intact, seems less rusty than the WP&Y 61 was, but that engine is being restored. I just wonder, if some of the mechanically inclined folk on here, could give me an idea of what condition these parts would be in, in terms of wreck damage, and 100 years of immersion in freshwater, would do to them, and what it would in theory take to make this engine steam again? I simply want to know this to understand how durable these locomotives are and how much a locomotive can take before it is deemed impossible to restore to operation. Could the engine in theory, be rebuilt with it's original "bones", providing a foundation for a new boiler, and other components? i am not saying this is practical or at all likely, but i simply wonder if it's possible from a technical standpoint, in a hypothetical scenario where funding and skilled workers was not an issue.

Not an engineer! Just an old survivor.
In the world of steam traction engines, I know of two pulled from lakes. It was generally felt, after the fact, that they would have best been left where they were.
There have been a couple of traction engines pulled from partially submerged locations and made to run again. A bulldozer was pulled from a swamp in Minnesota after several decades and was in surprisingly good condition.
This locomotive, and the one in BC are in deep, cold water and the metal might be better preserved.
In salt water, the penetration into, especially, cast iron, is very destructive, causing the metal to expand and "pop" -- I have seen that first hand in recovered items. In fresh water, there is likely some penetration of elements into the metal, but perhaps not to a fatal extent.
In the case of the Lake Superior 4-6-0, it also appears to have considerable damage from the tumble.
Anything can be restored if one has the money. As some people say, if it casts a shadow, there is still hope.
However, as discussed in the BC case, the effort and cost of a recovery might be better spent towards existing above-ground artifacts. There are a few D-10s sitting around that likely need some attention.
Also, getting anything done in Canada going forward will be difficult.
I was always told there is a Great Western loco buried in a "bottomless" swamp at Copetown, Ontario. It turned turtle in the early 1850s during construction of the line and became "rip rap" because it just kept sinking. Whether true or false, the present CN main line Dundas Subdivision runs over the same spot. After nearly 175 years, CN is still struggling to keep the site stable.
Here is an interesting article about sunken locos, with a fair bit about the Lake Superior one:
https://churcher.crcml.org/circle/Sunken.html

This is the second thread the OP has started on this subject this year--- can they be combined?

See

viewtopic.php?f=1&t=45325

BOb H

Not a locomotive but still steam recovered and restored from being under water for a while. https://m.youtube.com/watch?v=Ug6hmnUvTps

As has been said if you put enough money into it and replace enough parts anything can be restored.