OPTIMAX loosing rpm

[Newo]

Hi all I need your help, I have a problem with my mercury OPTIMAX 200 engine, year 2006. Engine has lost rpm, it usually runs between 5300 and 5400 Rpm at wot. Now it's maximum rpm is around 4200rpm, I have replaced spark plugs, fuel filters but problem remains. It also seems to get worse when I leave it on low revs for a while and then try to open throttle maximum rpm goes down even more to around 3400 rpm. Today I got my mechanic, he connected the computer and found no faults, he replaced some high tension leads and coils but still problem persist. One thing he noticed is when he hooked up gauges to check fuel and air pressure, pressures are ok both for air and fuel with ignition on but as soon as I turn ignition off fuel pressure drops down strait away to zero air pressure remains good. Any suggestions? Engine sounds perfect on idle. Another thing I noticed is that engine is using nearly double litres per hour at 3500 rpm then usual. It also seems to be making abit more smoke then usual. No petrol is visible on the sea surface.

Any ideas?

Thanks in advance for your replies

owen

[boats.net]

Have him check to if getting fuel in air rail and check tracker valves in fuel rail.