[jclark003]

absolutely correct. Overloading diesels, really at any rpm will shorten engine life, sometimes dramatically. hard to give advice without more details and knowing how far off you are.  a couple of quick things to do are check that your bottom is clean and you aren't dragging something in your running gear. Also check/replace fuel filters and air filters as either one can cause your engines to not achieve rated speed. excess smoke or soot may point to a mechanical issue and a visit from Cat especially if you are way off at the top and or the problem is progressing. 

If memory serves a 375hp 3208 is rated at 2800 so 2830-2850 is a good wot rpm range. 

Good luck.