I sold mine (which were 3116s, to be fair, but they are not a lot different) while they still had low hours, to someone who likes Cat engines and wanted them. It was expensive and time-consuming, but I am not sorry. Cummins has been building the same basic 6-cylinder diesels since the eighties, refining them as they go along. I don't know how many million B-series engines they have sold, but the fact that they are still in production tells you something. Even the new QSB engines, which now come in ratings up to 480hp, are based on the same basic block, although the head and induction and FI systems are different.
The only Cat engine that in retrospect seems worth a damn is the 3208. There are people who have had long service out of 3116 and 3126 engines. Well, God bless them, I'm glad for them, but driving around with the feeling of having two time bombs in the engine room didn't add to my boating enjoyment. There may even be a pair of decent 3176 or 3196 engines out there. I guess I just haven't heard about them yet. Like Ross Perot, I'm all ears....