Ac delco spark plugs

[jmadisonbiii]

When I began the boating season, my ‘98 7.4 Mercruiser didn’t seem to be operating at 100%-rpms low, about 4100, struggling to get on plane, etc. I installed OEM cap, rotor and plug wires, and NGK BPR6EFS plugs gapped .045. Went to the lake and it ran exactly the same. Talked to a mechanic friend who said I should be running AC Delco plugs. The engine cover said AC MR43LTS. I installed a set today and the improvement was dramatic: excellent hole shot and closer to 4800 rpms, 7 or 8 mph gain on top. I never would have believed such an improvement when switching one brand to another of new plugs.

 

[Bt Doctur]

they dont, you had a bad ngk plug

 

[Scott Danforth]

plugs dont make a difference, however since you changed everything, you could have had a bad plug or wire or cap

 

[Grub54891]

I prefer to use the plugs that the specs require. I know any Chevy based motor don't like champion plugs, but have seen ngk plugs work fine. Usually they require ac/delco plugs though.

 

[Bondo]

Ayuh,..... I run the AC Delco MR43T plugs, 'n put in either those, or the longer MR43LTS plugs in newer motors,....

I Don't use any of the high dollar fancy smancy plugs in any motor,.... The only up-side to 'em is longevity,...

Boaters in general change the spark plugs Waayyy to soon,...
Long before they're at all, "Worn", muchless worn out,....

I also put Motorcraft plugs in Fords,...
Jap plugs in Jap motors,...
'n Euro plugs in Euro motors,....

 

[kershawD]

I agree Bondo. I have built several small block chevy race engines in my time and have found that even with the high dollar fancy smancy plugs you can still get a DUD! I have even seen where a previous owner has installed a mix of brands in a motor before. it didn't run! I like to use OEM brands in everything I own. GM and chevy - AC delco. Ford- motorcraft .ect. whatever the manufacture recommends

 

[mr300z87]

I just wanted to add that MERC 454 Manual #16 list the AC-Delco MR43T Champion RV15YC4 or the NGK BR6FS as inter changeable, while the MERC all V8s Manual #15 lists AC-Delco MR43T and Champion RV8C for all V8 engines including Magnums. I personally like NGK but also agree with others above all should work fine it they are all firing.