Cummins Engine—Rebuild Or Replace?

Initially we were firmly in the rebuild camp, as were most of the experts we consulted. After all, at 6000 hours our engine is, in the words of David in his comment, “[a] baby and has many hours running [still] available”. Rebuilding would also save all the expense and aggravation of changing all kinds of things on the boat to make a  new engine fit. Not trivial in that the expense of such changes can run to half, or even match, the cost of a new engine.