I don't know about the 617, but the engine after it, the turbocharged OM603 was 600 something pounds with an aluminum head. The 617 has a cast iron head, but it's a five-cylinder. Hmmm.., I know it's heavy!
The OM615 was the non-turbo charged maybe 200D's of the 1960'S? Just a stab in the dark!
Anyway, I think they're the lightest OHC cast iron MB diesel. The OM617 is much bigger than the OM615, so it weighs quite a bit more.