[hookup44]

I have a 2002 4100 Open with Cat 3126B engines.  The boat was running fine and I had it pulled for a transducer and bottom paint.  A few days later I was heading offshore.  I had the engine synced and at 2250 RPM's, the port engine would not increase power; however, the starboard continued to operate normal.  I took the engines off sync and the port still wouldn't make more than 2250 RPM's.  Up to 2250 RPM's the engine runs fine.  Not under load, it would make 3000 RPM's.  The GPH on both engines at 2200 RPM's is around 14 GPH.  As I increase the throttle, the starboard RPM's went to 2550 and the port didn't change.  The starboard at 2550 RPM's was burring about 18 GPH, and the port at 2250 RPM's was burning 23 GPH.  The star showed it was 50% under load and the port showed 100%.

Work performed since issue:
Turbo replaced.
A mechanic put it on a computer and said the injectors and cylinders were good and suggested checking fuel.
The fuel line at the tank going to the Racor did have a clog.  I cleaned the line, rebuilt the Racors and polished the fuel.
I tried both fuel tanks.
I ran a line from the engine directly to a fuel can bypassing the filters etc.
I replaced a very dirty crankcase filter.
At idle and underway up to 2200 RPM’s, the return line has a small steady flow of fuel.  However, at 2250 RPM’s it completely stops.
There’s no air in the return line.
A diver checked the props and they appear to be fine.   
 
Notes:
There is no smoke and no fuel in the water while at the dock or underload.  
It starts and runs fine up to 2250 RPM’s then stops making power with throttle remaining. 

Today Quinn Caterpillar inspected the engine and could not find a problem.  

Has anyone experienced anything like this?
 

[Sans Peur]

Have you tried going to Boatdiesel.com ? You have to pay for a subscription but the knowledge on there is incredible.

[hookup44]

Have you tried going to Boatdiesel.com ? You have to pay for a subscription but the knowledge on there is incredible.

I have posted there and tried every suggestion.

[Sans Peur]

If it is using more fuel and still not gaining RPM's sounds like an air flow restriction. I read where you replaced the turbo. What does the turbo pressure do when you try and increase throttle? Have you inspected the air intake filter and adjoining hoses? On a diesel forklift I had a hose get weak and would collapse internally at higher rpm' s restricting flow.

Also check your oil pressure, the turbo is powered from that and a restriction could not allow it to spool up higher.

Next step would be to start looking at the exhaust side for any restrictions. Do you have straight pipes of mufflers? I have seen mufflers delaminate inside and cause a restriction.

Diesels have to be able to breath both inhale and exhale. If either is restricted even just a little it is going to cause problems.

[hookup44]

Problem resolved.
Caterpillar checked the engine and cut out each cylinder and said it was good. It was not. I checked the fuel PSI at the front of the motor and at the back. It had the correct PSI at the front and zero at the back.

I pulled the fuel injectors and had them inspected. 2 were frozen and 4 were not working properly.