2006 250 Hpdi running rich

What would cause a 2006 250 HPDI to run rich ( Fuel not oil). Everything checked out O.K. on computer at dealer even after taking it to the lake with the computer hooked up.
When we got back they pulled the plugs and they were showing that it was running rich. Also pulled fuel pumps checked them and checked out ok. Maybe the computer on the motor might be bad???? http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/crying.gif http://www.bassboatcentral.com/smileys/doh.gif

Throttle Posistion Sensor?

Computer said all sensors are within spec.

A leak in one or more of the mechanical fuel pumps diaphragms, allowing fuel to squirt directly into the crankcase area and be sucked into all the cylinders. You can inspect the mechanical fuel pumps for leakage with your eyes and nose. But you have to pull them off and look at 'em.
Other than that look at the fuel pressure regulator (just above the VST...) for leaking diaphragm. You should be able to put a vacuum tester on it and it holds vacuum. If you can suck fuel through it change it.
I assume the Yamaha tech using the YDS software checked that the temperature sensors were all functioning correctly, like the ECU doesn't think the motor is cold and running it rich on purpose.
Those are the only things I can think of that would get all 6 cylinders running rich.

You have a Racor installed in the fuel line right?


Mike