Merc 8.1L - Anyone use iridium spark plugs? What brand?

[highslice]

I went 10 years on the OEM spark plugs. Now with 5 years on the AC Delco platinum plugs the engine started misfiring this weekend under heavy load. I will start with the plugs, the wires are brand new. Hopefully it's not coils. Just looking for real world experience with iridium plugs. TIA.

 

[scoflaw]

Your pcm will throw a code if it's a coil. Merc used a GM coil 12558693, about $50.

 

[Pirate Lady]

I use Iridium in cars. The boat gets old fashioned AC MR43 somting or other.
Have never ever let me down. Coated with fogging oil from winterizing? Fires right up. Better than a Timex.

 

[Shenanigans77]

FIL 8.1’s seemed to eat the 983 delco’s every other season. Would start with a slight misfire at idle. Running the NGK TR55IX in it now for 3 seasons, no issue

 

[highslice]

FIL 8.1’s seemed to eat the 983 delco’s every other season. Would start with a slight misfire at idle. Running the NGK TR55IX in it now for 3 seasons, no issue

Just put these NGKs in this weekend (well my son did). Boat fired right up and ran like new. Full power back and no misfires. The AC Delco plugs that came out just looked worn out. I will say the NGKs negative post is a lot beefier than the Delcos and the NGKs were much harder to gap than the Delcos for that reason. Had to use a needle nose to open the gap because the plugs bent the tool on the gapper that is supposed to do that. Hopefully they last. My son has been running these in his Mazdas for years with no issues.