Volvo Penta D3-110, Warning check EVC system.

Hi everyone,
Wondering if anyone can help.
Ocqueteau 645 steaming along at 2750 revs when tachometer beeps and reads 'warning check EVC system', Tachometer falls to zero but revs remain the same. I come down to tick over and switch the engine off, then start up again whereby the tachometer starts working again and the warning disappears. I bring her up to 2000 revs where she sits happily for an hour until I increase up to 2750 rpm then within 30 secs tachometer beeps and warns check EVC and falls to zero(revs remain the same)
My EVC only monitors 5 conditions, Engine hours, Turbo pressure, Coolant temp, Voltage, and RPM.
Local agent here in Weymouth put Vodia tool on and it read unidentifiable fault, they said check all EVC connections (which I have done,including the two engine fuses) but to no avail.
I have run the engine out of gear for 15 mins at 3000rpm and no warning shows so my eyes are turning towards turbo pressure or coolant temperature.
Any help would be greatly appreciated guys...thanks.....Phil

Thanks for prompt response Capt J,
The boat has just had a full service from Volvo,all filters oils impeller and coolant were replaced, the coolant reads 86 degrees C at 2750 rpm.
The EVC alarm would tell me if the coolant were to hot,or indeed if there was a problem with the engine, but the engine runs beautifully'
The problem I have is with the EVC system itself, it reads 'Warning check EVC system'

Thanks guys for your help,
I'm from a marine engineering background so I'm pretty clued up on marine diesels and how they work.
My snag is the electronics of the EVC. The snag was there before the service, they connected their Vodia interrogation tool and it showed no faults on the engine, just an unidentifiable fault on the EVC system.
The problem I think is electronic, yet related to the change in the engine state as it approaches full power, which is what leads me towards temperature and/or pressure. It is not a mechanical problem because the EVC would register a fault to that effect.
So in short the engine runs perfectly, it's the EVC that cuts out as the engine gets close to full power, it's almost as if an EVC sensor is working loose through vibration or expansion via temperature rise.
The most relevant information is--
The engine runs flat out at 3000 rpm out of gear with no problem.
The engine runs in gear at 2200 rpm with no problem until I increase to 2400 rpm when the warning beeps within a minute.
Grrrrrr!
I will check out your suggestions ref earthing points etc.......Many thanks again

Cheers Fishtigua, that is great information, I checked out the turbo vanes and everything seems fine there.
I'm sure the tachometer dropping to zero is an attention seeker programmed in to to do just that, the engine does not miss a beat when the warning goes off.
I'm sure it is related to 'under load' conditions....thanks again for your help, I'll keep you all posted if I find the snag.