Cat engine loses rpms

[whaler23]

My 3160 (3208) Cat Natural on my port side(1400 hours) has begun to lose rpms after about an hour of running over the last three or four times out. I have replaced the primary and secondary fuel filters about two months ago (15 hours maybe) as well as attempted to rule out the tank by switching fuel source to the starboard tank. If I idle back after the engine loses revs and after a minute or so hit the throttles again it goes right up to cruising rpm for about 45 seconds or so then repeats the rpm drop. It only drops to about 2K rpms, cruise is 2450. Switching tanks does not affect rpm drop. Starboard engine runs fine on port tank, as does generator. So I think I have ruled out the tank, not sure about the filters at this point, I will switch these again next. Any ideas.

[SKYCHENEY]

Sounds like a fuel restriction. I would replace filters first and see if it helps.

[whaler23]

I agree with the fuel restriction concept, but why not right away, it shows up after an hour or so at cruise. What signs emerge when an injection pump starts to fail, etc... Not that I want to go in that direction.....

[jim rosenthal]

Sounds more like a governor problem to me....or FI pump, sorry Scott.

[SeaEric]

I have a good Cat guy here on the Chesapeake. PM me for his info.