KADP44 EDC supercharger engages and disengages please help!!!!

I have a GOBBI 375, 37.5’, 12 metric tons displacement, with 2 VOLVO PENTA KADP44 EDC. These motors were commissioned in 2001 and they have 340 hrs each. I have developed a puzzling problem with my port engine and I thought you guys may be able to help.
This is the sequence of events:
1.Everything is smooth until I reach 2850 RPM.
2.I push the throttles little more, (using full trim taps nose down) the engines reach 2950 - 3000, (18 – 19 knots).
3.The port engine’s supercharger disengages, and then it’s engaging again, thus loading the engine, which makes it drop down to 2700 RPM (14 – 15 knots). If I keep the throttles steady the supercharger engages and disengages continuously.
4.When this happens to the port engine, the Star port engine gets overloaded, the rpm drops and the supercharger engages.
5.The whole circle continues until I retract the trim tabs – nose up and then I hear the clutch of the supercharger of the port engine to engage disengage couple of more times.
6.From this point on the rpm goes up and then continue to rise to 3000-3100 and stabilize the speed to 23-24 Knots.
7.Now, I can increase the revs normally with no problem.

Did anybody have a similar problem? Do you know what could be the problem?

My certified VOLVO technician insists that I need a new turbo; he tested the engines and he says that he found out that the port engines’ turbo makes 2 psi less pressure than the specs. But he also said that the turbo spins freely which makes me having doubts as to whether the turbo is the problem.

Also I would like to ask if anyone has the electronics workshop manual for the KADP44 EDC engines.

Thanks in advance,

George

After reading your symptoms I guessed that your turbo would be low on boost. We had the same problem on a KAD32 which has the same supercharger/turbocharger setup. The Volvo tech has probably made the correct diagnoses. The problem is not that the turbo won't spin, it is that the tip gaps between the vanes and the housing get too big either through hours run or through age/corrosion. It then can't make its boost. Our experience with the KAD32's was that the turbos were good for 1500 - 2000hrs, but yours are older (in years) and may have suffered from corrosion wear.
At 340hrs however I would be suspicious about the turbo going out of spec, so I would carefully check the piping from the turbo to the inlet manifold etc for leaks, and also that the bolts/nuts holding the inlet manifold on are all still tight. An air leak in the manifold or anywhere between the manifold and turbo can cause the same problem. We fixed a leak on one of the rubber 'connecting' hoses between the turbo and manifold just a couple of weeks back. It can certainly happen.