Who's good at reading spark plugs?
LaRea
Member, Moderator Posts: 7,826 mod
Anybody want to offer opinions on what these spark plugs say about the health of my engines? @212rowboat, @69fastback ?
2007 Rinker 370
Merc 496 engines with 800 hours
Plugs have 300 hours
[EDIT: plugs are AC Delco 41-983, platinum plugs]
After replacing plugs and wires this weekend, I noticed an immediate bump in performance. Cruise MPG improved by about 9%, getting back up to what I recall seeing a few years ago. I attribute the improvement to the wires, not the plugs. The wires were probably original, and two wires had severe chafing damage.
A few things I noticed about the plugs:
2007 Rinker 370
Merc 496 engines with 800 hours
Plugs have 300 hours
[EDIT: plugs are AC Delco 41-983, platinum plugs]
After replacing plugs and wires this weekend, I noticed an immediate bump in performance. Cruise MPG improved by about 9%, getting back up to what I recall seeing a few years ago. I attribute the improvement to the wires, not the plugs. The wires were probably original, and two wires had severe chafing damage.
A few things I noticed about the plugs:
- S8 is cleaner than the others. That's one of the plugs with a damaged wire. It's possible the plug was not sparking at all.
- S4 is a little bit shiny. Oil fouling?
- P3 has some crusty buildup on the side of the insulator.
- P7 has corrosion on the outside ... maybe a water leak that I need to investigate.
Post edited by LaRea on
Comments
My speciality is 2 cycle so I only worry about grey plugs(lean) i want charcoal wet ground straps. No valves or oil rings to worry about.
Ill also be following this thread closely.
How do the efi motors do at idle/trolling speeds vs carbed? Even with my Holley dialed in by one of the best in the carb industry i still needed some wot after long idle times to clean the plugs.
I did the plugs when I got the boat from someone who probably couldn't spell maintinince and they looked all normal and matched.
Did it have a probe in the intake or engine mount fuel filter assembly? Usually they have some place to heat fuel or air when operating at or near freezing temps
A guy picks them up for food or maybe bait. Once they warm up they come to life and go ape $hit all in this guys car and causes him to wreck.
PC BYC, Holland, MI
500 hrs on a set of plugs sounds about right on new efficient efi motors. 300 wouldn't hurt.
Florida ain’t the paradise Floridians want it to be...
Regards,
Ian
The Third “B”
Secretary, Ravena Coeymans Yacht Club
https://www.rcyachtclub.com/