Changed plugs. Old ones looked ok now new ones look lean.

[LAC_STS]

I took the Autolite plugs out of my engine and put NGK plugs in. BR6FS which members here said was what to put in so Im sure theyre the right plug.

The Autolites looked normal when I took them out. Not rich and not lean.

I only have about 10 hours on the new plugs and today I took one out to see what they looked like and they were all very white.

Its hard to see on the pics some of them but its hard to get the camera to focus on the plug but you can tell they are very white. What would cause this? Nothing has changed but the plugs. How could the old plugs look fine and the new ones be white?

One of the pics ( I think the first one) you can see the plug looks weird. It has little holes on it and just don't look right.

The pics are of all different plugs. I didn't pull them all. Just 1, 3, 5, 2 and 8.
they are alot whiter in real life than in some of the pics. If needed I can bring my DSLR down to the boat tom. These pics were took with my Iphone 4.







thanks

 

[airdvr1227]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Someon here will know better than I but the recommendation of plugs by members is suspect. Sounds like you've got too hot a plug for your engine.

 

[Gary H NC]

Re: Changed plugs. Old ones looked ok now new ones look lean.

OMC with the GM based engine never called for NGK plugs.They came factory with AC plugs.
AC MR43T
You can get them from Rockauto.com very cheap.
Napa can get them but want about 6 bucks each.

I have had engines run terrible with new NGK plugs...put the old ones back in and it ran fine...

 

[LAC_STS]

Re: Changed plugs. Old ones looked ok now new ones look lean.

AC MR43T crosses over to the same NGK plugs I got now. I will see if I can compare the heat info when I get home.

The engine runs fine and like I said the old autolite plugs were fine looking. I replaced them because they're autolites and they were rusted pretry bad after only 2 months.

 

[airdvr1227]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Well, the other thing I've learned recently...if it ain't broke...don't fix it.

 

[Moggy23]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Those plugs look fine and are not too hot, ignition timing is good too.

 

[Aloysius]

Re: Changed plugs. Old ones looked ok now new ones look lean.

There's a color change line on the ground electrode, so the heat range is ok. I think you're ok..if the plugs were pulled shortly after you ran it at cruise. If it's been idling, it looks too hot/lean.

 

[John_S]

Re: Changed plugs. Old ones looked ok now new ones look lean.

If it's been idling, it looks too hot/lean.

Which would be an idle mixture adjustment not a plug problem.

 

[Gary H NC]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Every plug is made different.Most parts stores seem to push the NGK brand.
Myself,i would stick with AC plugs.Better quality than NGK in my opinion.

I know that on some outboards like the older Johnson-Evinrudes they call for Champions.I hate Champion plugs but those motors run best on them.
I had one customer who bought NGK plugs for me to install,He brought the boat back and said it run like crap..I put Champions in it and problem solved.

Just saying,sometimes the brand can make a difference...

 

[John_S]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Every plug is made different.Most parts stores seem to push the NGK brand.
Myself,i would stick with AC plugs.Better quality than NGK in my opinion.

I know that on some outboards like the older Johnson-Evinrudes they call for Champions.I hate Champion plugs but those motors run best on them.
I had one customer who bought NGK plugs for me to install,He brought the boat back and said it run like crap..I put Champions in it and problem solved.

Just saying,sometimes the brand can make a difference...

In this case, there is not a performance problem being noted. Merc has specified the AC and NGK in equivelent engines. It is unlikely to be causing any difference in this OMC. I never had a problem with AC or NGK. NGK's are easier to find for me locally, than the marine AC's. The op can go ahead and change to AC, but will probably stand more of a chance cracking a plug vs any difference in performance.

 

[LAC_STS]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Well, the other thing I've learned recently...if it ain't broke...don't fix it.

If I had left the Autolites in there they would be rusted stuck by winter and two of them had cracks all the way down the porcelain.

There's a color change line on the ground electrode, so the heat range is ok. I think you're ok..if the plugs were pulled shortly after you ran it at cruise. If it's been idling, it looks too hot/lean.

I did make a 5 or 6 mile run back to the dock at about 3/4 throttle, but before I get to my dock I have to go through about a 15 minute no wake zone.

I will be going to the boat today and I will let it idle to see what the plugs look like. Ill try to get some better pics too cause they are a lot whiter than they look in the pics. I could be wrong but Ill do it just in case.



Thanks everyone.

 

[Gary H NC]

Re: Changed plugs. Old ones looked ok now new ones look lean.

In this case, there is not a performance problem being noted. Merc has specified the AC and NGK in equivelent engines. It is unlikely to be causing any difference in this OMC. I never had a problem with AC or NGK. NGK's are easier to find for me locally, than the marine AC's. The op can go ahead and change to AC, but will probably stand more of a chance cracking a plug vs any difference in performance.

True...As long as it runs ok it should not be an issue.
I have never seen a Merc manual call for NGK plugs so something new i learned..
I know OMC never called for anything but AC plugs in the GM engines.

I was thinking about the local parts houses near me...they always push the NGK brand for some reason.

 

[bruceb58]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Looking at plugs after idle doesn't tell you much. Your idle circuit could be way rich and your high speed circuit could be too lean yet your plugs would show rich. You want to read plugs after a high speed run.

 

[LAC_STS]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Looking at plugs after idle doesn't tell you much. Your idle circuit could be way rich and your high speed circuit could be too lean yet your plugs would show rich. You want to read plugs after a high speed run.

K Ill try both and report back. I just dont understand how the Autolites can look normal and these dont.

 

[JustJason]

Re: Changed plugs. Old ones looked ok now new ones look lean.

You want to read plugs after a high speed run.

Agreed.

The only way you can really read a plug is by going out and doing a WOT run for a good 10-15 minutes, then bring the throttle down and shut her off quickly. You don't want to idle around for a few minutes, you want to get off the throttle then shut it off.
Then give it 2 or 3 days and pull the plugs. If you have any small water injestion problems it will show up as rust on the plugs. If you have a large water injestion problem you'll get rust plus steamed clean white porcelan.

 

[LAC_STS]

Re: Changed plugs. Old ones looked ok now new ones look lean.

I have to wait 2 or 3 days before pulling the plugs? I pulled them 5 mins after I got back last time.

 

[John_S]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Here is a link to the original thread which includes pictures of the autolites: http://forums.iboats.com/showthread.php?t=435665

 

[LAC_STS]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Here is a link to the original thread which includes pictures of the autolites: http://forums.iboats.com/showthread.php?t=435665

Oh yea, thanks John. See dont the autolites look normal? That plug with the crack on it actually has 2 more cracks on the other side. One of the other plugs has one crack.

 

[John_S]

Re: Changed plugs. Old ones looked ok now new ones look lean.

Oh yea, thanks John. See dont the autolites look normal? That plug with the crack on it actually has 2 more cracks on the other side. One of the other plugs has one crack.

Actually, it would be nice to see more of the ceramic part of the tip and from ones that were not cracked.

Also, would like to confirm that no other changes were made outside of the plug change, such as carb tuning/adj, timing, exhaust elbow/manifolds, etc. I know you have had allot of posts and have been working issues, but have not tried to keep any list. When you last did the idle mixture did you tune toward the lean or rich side?

Cracks mainly happen on installation and removal. With the larger cermanic of the autolites, and typical exhaust manifold clearances, I could see how that can easily happen. I cracked a few on my first plug change.

Now, how a crack will impact the performance of a plug, I don't know. I suspect that the electrode is intact but the heating/cooling of the plug is impacted.

The NGKs are the right cross to AC's, so you have the right plug. I think the question is now, is there something else not working correctly? Plug reading is not what it use to be. All the gas additives, and now the alcohol help keeps thing much cleaner. I would just keep a close eye on things, and keep checking them until end of season. If you notice any metal errosion etc, then that would be cause for alarm. If water is steam cleaning them, you have leaks.

PS: I think Jason's comment about the wait time is for the rust to form on plug.

 

[LAC_STS]

Re: Changed plugs. Old ones looked ok now new ones look lean.

I am going to the boat in a few and will check and take more pics.

Nothing else has been done to the engine except the plug change. I fixed the problem I was having by installing a ballast resistor for the coil and ran another 15 hours or so on the autolites. Then I changed to the NGK's.