3.0L Spark Plugs....again.....

[Bonanzadave]

Re: mercruiser 3.0 lx spark plugs
cause i heard that if its a est or digital ignition and not a plain points ignition the reach of the spark plug will matter


Type of distributor has nothing to do with which spark plug you use. It all depends on what the head was designed for. The 3.0LX uses the longer reach plugs, so you would use the AC MR43LTS plugs. you can also use the NGK BPR6EFS.
I wouldn't use champion plugs on any marine engine. To high of a failure rate for me.

Just whippin a very old horse...

Got the AC R42s called out for on the engine cover. They didnt have the MR42s but they did have the MR43s. I see no difference (dimensionally) between the R42s and the MR43s.

Comments......

 

[Rick Stephens]

When Chevy went through its Vortec upgrade, my understanding is they did the same to the 3.0L head as well to improve flow. The R42 and R43s are different temperature, not different length. I believe the longer reach plug is the MR43LTS. The shorter reach was MR43T for pre LTX motors.

 

[alldodge]

There is some differences showing up

Your serial number shows plugs as 33-816336Q and pictured is NGK BP7HS10
https://www.mercruiserparts.com/bam/subassembly/30910/2330/50

Manual 26 1998 and up 3.0 list

AC - MR43LTS
Champion - RS12YC
NGK - BPR6EFS

AC plugs the number goes higher with heat range - 42 is colder then 43
NGK plugs do the reverse - 7 is colder then 6

What ever plug do use marine (nickle plated plugs) MR (trivalent plating) NGK

 

[Bonanzadave]

Thanks guys ! I put the MR43LTS in. Will see how she does......