Dropped RPMS

1989 43 with 671 TIB's, I have seen it turn both 2400-2450. Bottom was inspected and cleaned and props look good. I have dropped down to 2100 on both engines at WOT, speed is way off of course as well, very little black smoke even when I get on the throttles heavy. One puff of smoke and it goes away at one second and then only hits 2100 on both. I just changed the primaries and secondaries, also removed air filters and cleaned them. In neutral , I am seeing 2575-2600 dead racking in neutral. Can anyone provide me with any potential issues that I have not thought of yet? Your help as always is very much appreciated.

Thank you , did that cure the RPM issue for you?

Diver was on boat twice last week said we are good on running gear and bottom

All GREAT points but here is a more detailed description, nothing changed since it last made 2400-2450 WOT, in fact I have taken some weight off of the boat. The boat performs like a naturally aspirated diesel as I do not hear the turbos spooling up on either engine. There is virtually no "black smoke" at any time indicating that the fuel is just not there. I have zero running issues other than RPM turns. No vibrations, no white smoke, no blue smoke, temps and oil pressures are all in the same spot , no issues other than RPM's. I feel as though it is not getting enough fuel and that it might be some sort of linkage or governor adjustment.

Both primaries and secondaries are brand new, I am replacing them again tonight and inspected turbos to see if they spin freely . I am leaning hard towards a bad batch of fuel , that is the only thing that has changed since we last ran boat, no other mechanical work whatsoever. And again, zero black smoke, no white smoke, no blue smoke, all indicates fuel starvation. Oh yeah, no turbo spooling sounds either. It is like both turbos are not engaging, another example of no fuel = no boost.

It is a newer load of fuel, did not run boat much in the last couple of months and then took on additional 250 gallons of new fuel. Then started running the boat and noticed the sluggish, lost RPM issue.

Primary filters are Racor 2020 30 micron filters and the secondaries are the canister type that go onto the engine, cant recall their number but as I recall they are 10 micron filters that go into the metal housings.

Greg Page , did that solve the missing RPM issue when they did the rack adjustments? Odd that it has happened at same time to both engines, really leaning towards nasty fuel load. Going back to change all filters again tonight and re run it tomorrow . I will let you know if the filters look bad tonight. Only ran for roughly 20 minutes on these filters so far.