MTU Series 60 Won't Rev Over 1500 RPM

Check your fuel filters on that side.

When’s the last time you had the fuel filters changed, how many hours on them now?

Sounds to me like you have a sensor slowing the rpm because it "senses" something wrong, and this is a protection/get home feature. Put a computer on it.

Do the MTU Series 60s have the DDEC displays? Any codes? What are the boost pressures and air intake temps at 1500 rpm under load? Any black smoke under load?

If you're running 30 microns in the racors it's most definitely clogged secondary fuel filters. Since the switch from High sulfar offroad diesel to Low sulfar offroad diesel, I've seen on 3 different relatively new yachts have issues with the displays showing low fuel pressure, the 30 micron racors looked almost clean and the secondaries were plugged. I only run 10 micron filters in racors on everything now. I'd rather take 20 seconds at sea to change a 10 micron racor for $15 than mess around with secondaries, filling, changing, priming, etc. I'd start there.

Were there any codes at all? If not it might not be fuel filters at all, I'd take a hard look at aftercoolers and also change them if they haven't been changed in the last 7 years or so......or the throttles themselves, could also be batteries and/or battery voltage. In your situation it's best to get a DDEC tech out with the computer.

I’ve had this exact same problem several times with series 60s on an ocean 50. Check the black pressure sensor on the aft end of the aftercooler. It can get condensation water or debris in it which can cause the engine to derate. It comes off with two 8mm bolts. If water comes out of the aftercooler or sensor after you take it out this is almost assuredly the problem. May need to clean the aftercooler condensation drain lines too.

Be nice if we heard back from the OP?

63-64 psi sounds low for fuel pressure, but I can't remember what Series 60s run at. I always run 10 micron fuel filters, they may get dirty quicker than 30s but better than secondaries getting dirty. I'd change the secondaries if you pull them off.

Will the engine make rpm's in neutral?

I have seen 3 different almost new boats with fuel pressure issues in the past few years to the point the computers were alarming. 2 different manufacturers, yachts under a year old, 1 still owned by the manufacturer and another a customer boat. All 3 had fuel pressure alarms, showed low fuel pressure on the display and on all 3, the 30 micron racors looked almost perfectly clean. All 3 of them had plugged secondaries. 2 CAT yachts and a VOLVO IPS yacht. The lower sulpher offroad diesel breaks up the algae particles into smaller particles than 30 microns and they completely bypass the 30's. CAT, MAN, and Volvo request 10 micron fuel filter elements in the primary filters (nobody enforces this from what I've seen). I sure as heck would rather spend 20 seconds changing a 10 micron filter that's dirty, then mess around with fuel and changing secondaries in a hot engine room.

Yanmar, CAT, and most others are running a 2 micron secondary these days.

Here's some info on fuel system data for a S60. Converting in. Hg and your Vacuum measurement of 9 psi seems high, 12.2 in. Hg is 6 psi maximum for a dirty system.

It sounds as though the DDEC governor has activated Smoke Control, which means it is reducing fuel delivery. Smoke Control and Fuel Pressure do not show up as separate codes, but you can have your guys look at the engine related boost pressure issues. After talking with some knowledgeable S60 guys, lack of turbo boost can be due to the following:

1. A damaged compressor or turbine wheel, would require replacement.
2. The Charge Air Cooler (CAC) air fins could be contaminated. They would then need to be removed and cleaned in an ultrasonic solvent tank.
3. The old style fiber intake manifold gasket is leaking, they should be replaced by metallic ones.
4. The CAC gasket is leaking air, you can see if the gasket is pushed outside of the gasket surface area. If so, replace the gaskets (2).
5. The compressor to CAC housing J-tube is leaking boost on the bottom side, usually pin hole leaks, and if so, the tube will need to be replaced.
6. Easiest - the boost pressure sensor measuring passageway has salt build-up or has water in the sensor passageway. Clean and remove water.

Hope it helps.