1985 50 HP lower unit bearing

Long story, hopefully short.
I removed lower unit and gave to a retired mechanic who specializes in Johnson/Evinrudes to find source of shavings. Found few teeth chipped on pinion.
Found an issue with the tapered roller bearing on the shaft below impeller pump. The bearing that was installed had a broken outer race.
I ordered a new Timken, found that there's a lot of clearance between outer race and aluminum case. He ordered another bearing, same exact issue.
There's no obvious milling marks as if the bearing had spun or anything. It appears as if it's original surface.
Mechanic said he's never seen this in 40 years. He's stumped.
Anyone ever ran into this?

It's possible that some other model lower unit has been installed on your engine (it happens).

Pictures and a accurate description would be a big help with this problem.

The bearing housing that attaches to the lower unit just under the water pump, attached with four bolts..... is it round, square, what? Does the bearing sit within this housing or within the lower unit itself?

Detail 48 on diagram. I dont have the photos since changing phones, sorry.
Thanks for your reply, I had pondered the different LU idea.

I checked my books... I assume you're speaking of the 385175 roller bearing (not the flat thrust bearing). That's a good number and NOT superseded up to any other number. If this is the number that your mechanic is ordering and receiving, I can only assume that perhaps that bearing seized and spun within the gearcase housing which would create the filings/shavings you mentioned and the increased bearing race clearance.

If so... picking up a good used gearcase would be the next step.

Fairly common on that " less than robust " gearcase.---Perhaps the bursting / cracked bearing expanded the housing ?----Replacing the entire gearcase with a torn down / inspected one is the best option here.