low_psi

Have been having issues with excessive soot and a minor mis while under heavy load. Boat still runs excellent once up on plane and has no issue reaching it's peak RPM and speed. I have been thinking my issue is with Fuel Injectors. Had a guy tell me it also puffed a small bit of smoke when the mis was present. I ran a cuple of bottle of FI cleaner through it and the soot does seem to be clearing up. I changed the plugs Friday and it also feels like the mis may have gone away.

These plugs have been in for about one season. They are in order the way they were in the motor (if looking a it from back seat). I took 2 pics, one of the cleanest side of each plug and then flipped them over to get the dirtiest side of the plug. Looks like the dirty side was the side exposed to the fuel injector?? Anyway, what do these plugs say to you engine experts?? The lighting appears to have been bad in the photos, they are not nearly as dark as they appear in photo.... Engine is 496 mag (non-ho).

Unlimited jd

Need to cut the threaded portion off so we can see the base of the porcelain

low_psi

I can do that... But how would I do that? Never really cut one before. Just a cut off wheel at the base of the threads (obviously cutting around and not through...)?

Budman II

From my (admittedly scant) experience, the plugs won't tell you much. Since the boat has been run at idle, part throttle, maybe even WOT at different times over the course of a season, you won't be able to tell much other than early signs of detonation, which would be exhibited by flecks of aluminum on the porcelain, melted electrodes, etc. None of that is obvious in the pictures. Plug readings have to be done with a full or part throttle run on a new plug with immediate shutdown - don't let it return to idle for any length of time. As red posted, the coloration ring would then be found at the base of the porcelain. There are people who have been reading plugs for many years who will tell you that it is an imperfect science, especially with the ethanol and oxygenators in today's fuel.

If this is an EFI motor wouldn't you expect some codes to be thrown by the ECU if you are having a misfire or injector problems?

Griff

The plugs say its running rich, but all merc engines are set up rich. I haven't seen plugs from any other 496's to tell if those are darker than normal.

low_psi

It is definatley rich, as evident by the soot on the transom.... I guess I am hoping some one can magically say "looks like a bad injector in cylinder #"... I know that isn't the case, but would be nice. I think I will pull the plugs on Friday (ran it one day on new plugs) and look at them. See how things look. I am really hoping it was a dirty injector, but things are never that easy...

BajaDan

+1 on this. No lead gas and now ethanol make plug readings very difficult. And to do it correctly you need new or freshly cleaned plugs, run at the condition you are trying to evaluate, then chop the ignition and pull the plug to look at it. Tough to do on a boat. Having said that mine look just about like this (496 Mag also) when I pull them out.

It does look like a couple of them could have an excessive gap. Measure that and set to the Raylar recommended 0.050 gap (stock is 0.055).

Dan

low_psi

I put all new ones in at .050. I will check the gap on the old ones tonight.

FIXX

Looks like you burn premimum...

low_psi

90 octane free, that's what is at the docks. But it was actually tuned by whipple to run 93. But because it runs so rich, I haven't run 93 in a long time.