Baker nailed it. 3208 not pumped up too high or run too hard does very well in boats. Trawlers with 210's, 300's, 320's, 375's, Bertrams et al with 300's, 320's, all do well. A 375 run hard does ok, but there have been failures. 425's and 435's run hard don't last.
The Cummins B came on the scene when the 3208 was already well established. And when the B came out they really did not hold up. The 250 and 300 were failing all over the place in the late 80's and early 90's. But Cummins stepped up and helped a lot of boat owners that had failures, even out of warranty. That helped the brand from getting too much bad mouthing.
Then they came out with the B 330 and 370 in the mid 90's. We figured there is no way these things will live. But they did. Cummins learned much from the early failures and fixed them. I doubt you can run a 370 hard and get 5000hrs, but some have. And run easy, they go and go. Us gear heads have also learned much, and now have got "care and feeding" for the B pretty well figured out.
But a 3208 at 320 requires little attention compared to a 330B. Both considered excellent engines. 3208 might need head gaskets, and don't let the oil pan rot. The B needs aftercooler attention or it might bite you. B loading more critical due to the smaller displacement. Don't cook either and keep them dry. And motor on and on.
