All insulators white on port 500EFI. No detonation codes present. Should I be worried? Will check fuel pressure, barring bad injector, can pressure be adjusted. Merc Maint manual vague on subject.

w/ properly calibrated efi, insulators will be nearly white... thats how it works... perfect mixture w/ perfect combustion. take a magnifying glass and look at the edges of the center post for erosion or tiny dots of metal... that will tell you if detonation present.

Starboard engine insulators are the tan color that I have always associated with good combustion with a slight safety margin just on the rich side of peak egt. As for perfect combustion and perfect mixture, that alot more credit than I be willing to bill to MEFI-3.

I'm with you. I would feel better with a tan color. Too lean can do some real damage. How's the performance?

ok... so you would like some more color... how much ? simple fact of the matter is that if all the plugs are white to the point of scaring you then the entire system is lean... which , since you say there are no codes the sensor array must be i ok, and , if so, then your lean condition is because the fuel pressure is low. any bad sensor that would send you lean enough to scare you visually... and thats all we are talking about here because there is no empircal evidence like high egts or detonation warnings or erosion or metal deposits on the plugs or reduced performance to suggest that it really IS lean would show up as a out of range code... if the pulse width is correct and the the fuel pressure is low then , yes... it would go lean.... but i would expect you to see that on your fuel pressure guage... as in the motor that you LIKE the color of the plugs on vs the one you don't...

for the record, on the best normally aspirated injected , efi motors where we got the ring seal correct, the plugs would come out snow white until the rings started to degrade or the fuel itself introduced the color. detonation was always very easy to see on the plugs with a glass.

I was under the impression that reading plugs by the color is no longer valid because todays fuel are cleaner, and the better way is to read the ground strap and the burn ring???