Broken cranks on OM 61X engines are fairly common, if the crank wasn't reground correctly.
The fillet radius on the sides of the bearing surface is critical.
If it isn't done to specs the crank can brake after a short time of operation.

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76 240 D. Bought in 1998 for $25.
85 300D. Got it for free with a bad engine. ( Sold )
60 Unimog 404. What was left of it, was given to me. Now powerd by 617A.
88 560 SEL. Bought without engine and trans. Now powerd by 617A.
67 250 SE. Cuope. For resto or sale.
64 220SE. For resto.