One of the technicians that I work with had a similar problem on a C-7 engine in a fishing vessel. The root cause of the problem on that vessel was a failed aftercooler core that allowed sea water to enter the cylinder head intake manifold and damaged the intake valve seats. That engine performed exactly like what you are describing, it lagged behind the other engine on acceleration, had alot of black smoke on acceleration, but ran fine when it finally came up to full load r.p.m. When the aftercooler was removed there was a considerable amount of soot build up in the intake of the cylinder head.
United States / Canada
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