Yamaha 300 HPDI engine problems- HELP!!

[Exodus]

I have a Regulator in the Bahamas fitted with twin 2004 Yamaha 300 HPDI which has been running fine until now, 540 hours both engines.

a problem has just developed with 1 engine.

will not idle out of gear and stalls, belches smoke when first started, 20% down on engine revs and power for same throttle as other engine, and consuming 30% more gas than other engine at identical RPM.

plugs changed with no effect.

yamaha dealer and technician cannot identify any fault, even with Yamaha diagnostic tools!!

anyone had a similar problem, and what was the cause??

[LegendMan]

Unless already done I would start with a compression test. Was that done? I would think a tech would have done that but you did not mention if it was checked.

[spider1]

Also need to start checking filters and connect a pressure gauge to the top of the VST and see what kind of pressure you have at the medium pressure fuel pump,

[Special K III]

There was an update on the "TPS Sensor" to raise the voltage from .55 to .58. My motors were stalling at start-up and then when this update was done (a month ago) the stalling stopped. I can't answer the question about your fuel consumption however....

[ghind]

Follow the sticky for your low pressure fuel pumps. They will cause excess fuel consumption, smoke and a blown engine... It is a quick check and I'd do it before using it again