Which spark plugs????

[jak2108]

I have a 1990 4.3L Mercruiser. We bought it at the end of last season and noticed it was quite difficult to start when cold and would sometimes miss a little until warmed up. So I am giving it a service before this season starts. I checked the manual and the type of sparkplug which was recommended was champion RV15YC4. I have ordered these but when I have now taken out the existing ones they are NGK BR6FS. The part which worries me is the electrode on the champion ones are about 4-5mm longer than the existing NGK type. I am worried that if I replace them with the champion ones, will the top of the pistons crash with the longer electrode on the new plugs?

Can someone help??

 

[achris]

Re: Which spark plugs????

The NGK BR6FS are the best plug for those engines. I refuse to use Champion any more... too many DOA...

Champion website says RV15YC4. But as I said, I won't use them....

 

[Bondo]

Re: Which spark plugs????

Ayuh,... I use AC Delco MR43T plugs in mine...
Which is the marine plug for any Chevy motor up to 96...

I wouldn't use a Champion either...

 

[Fishermark]

Re: Which spark plugs????

Ditto:

I realize this can turn out to be a case similar to "I use brand X of motor oil and love it...." But I ditto the ditto.

AC Delco MR437 is the way to go.

 

[PiratePast40]

Re: Which spark plugs????

OK - I'll stick my neck out there. I've heard several experienced posters say they don't like Champion spark plugs. There must be a common experience. Care to share so the rest of us don't blindly walk into the minefield? Please don't get me wrong - not being a smart azz. Really want to know what to look for.

 

[Bondo]

Re: Which spark plugs????

OK - I'll stick my neck out there. I've heard several experienced posters say they don't like Champion spark plugs. There must be a common experience. Care to share so the rest of us don't blindly walk into the minefield? Please don't get me wrong - not being a smart azz. Really want to know what to look for.

Ayuh,... In addition to what Bubba said,..
Years back, Champion had a nasty problem with the porcelain part of the plugs Shootin' free of the base, while under power...

 

[jak2108]

Re: Which spark plugs????

Thanks for the replies. The problem is I have already bought the champion ones. I just want to know if it would be safe to use the champion ones. I have read elsewhere that the longer tip plugs run at a higher temperature and are ok to use at low speeds and rpms. Due to the plug operating at a higher temp it reduces the possibility of plug fouling and helps starting when cold. However, if used at continuous wot it is possible to melt holes in the top of pistons. Is this information correct? I use the boat for skiing so never go wot. We ski at around 2000 - 2500rpm.

 

[Bondo]

Re: Which spark plugs????

Is this information correct?

Ayuh,... That's True... Bring 'em back,+ get the Right plugs...

 

[jak2108]

Re: Which spark plugs????

I dont understand why the manual suggests either the MR43T or the champion RV15YC4 if the champion ones could damage the pistons??

 

[Bondo]

Re: Which spark plugs????

Hey,... It's Your boat,... Do whatever you Want....

You came here,+ asked for opinions,+ you Got 'em....
What you do with the newly learned Info is entirely up to You....

 

[Fishermark]

Re: Which spark plugs????

I dont understand why the manual suggests either the MR43T or the champion RV15YC4 if the champion ones could damage the pistons??

Have you laid the Champions and the AC's side by side and compared them? If you are saying the Champions have a longer reach... then I'm not sure what to say.

 

[jak2108]

Re: Which spark plugs????

Bondo
I do appreciate everyones comments but I want to cure the problems I have when cold starting. I am unable to source the AC MR43Ts in the UK so would have to use the NGK or champion equivalent and like I said the info I found says that the lower operating temp plugs i.e the AC MR43T's or the equivalent NGK BR6FS could be the reason I am having the problems. So to change the plugs with the same type is just going to cause them to foul up again and ruin a new set of plugs.

Fishermark
I have compared them and yes the champion plugs have a longer electrode that is why I dont understand why the manual lists them?? I can only assume the manual suggests these 2 types of plugs if the boat is being used regularly at certain rpm. What I mean is does the manual suggest to use the MR43T (lower operating temp) if the boat is being used regularly at higher rpms and the champion ones (higher operating temp) if the boat is being used at lower rpms?? I have done some research and the NGK equivalent for the AC MR43T is the BR6FS and the champion equivalent is RV15YC4 but the champion equivalent of the BR6FS is RV9YC??? I just want to use a set of plugs which will cure my starting problems but be safe for the engine. How can changing a set of plugs become such a problem.

 

[achris]

Re: Which spark plugs????

Does your engine have a 2 barrel carb or a 4 barrel carb? If it's a 4 barrel, is it a Weber? Can you post the engine serial number?

Chris.....

 

[jak2108]

Re: Which spark plugs????

Hi Chris

These are the numbers for my engine and drive

Model: MCM 4.3L
Engine Serial No: OC856945
Transom Serial No: OD570252
Drive Serial No: OD558119

I am not sure if it is a 2 or 4 barrel carb I will take a look and get back to you

Thanks

 

[jak2108]

Re: Which spark plugs????

How can I tell if its a 2 or 4 bowl carb?? ( might be a stupid question).

 

[Don S]

Re: Which spark plugs????

How can I tell if its a 2 or 4 bowl carb??

They are called barrels, not bowls.

Take the flame arrestor off and count the number of round holes.
Better yet, take a picture of it and post it here.

 

[GopherPride23]

Re: Which spark plugs????

What about Autolite? The cross reference from AC-Delco to Autolite is a 144 or 145...what do you guys think about the Autolite brand?

 

[achris]

Re: Which spark plugs????

Hi Chris

These are the numbers for my engine and drive

Model: MCM 4.3L
Engine Serial No: OC856945
Transom Serial No: OD570252
Drive Serial No: OD558119

I am not sure if it is a 2 or 4 barrel carb I will take a look and get back to you

Thanks

Shows up as a 2 barrel....

 

[starsnstripers]

Re: Which spark plugs????

MR43t here too, 88 4.3 4 barrel > Had a full season on them never hesitated.

 

[Lou C]

Re: Which spark plugs????

MR43t here too, 88 4.3 4 barrel > Had a full season on them never hesitated.

I use the AC MR 43 in my old '88 4.3 and it's always been a good starting and running boat..and as far as Champions...well my Jeeps came with them from the factory...my 98 has had em its whole live {125000 miles) and I changed em every 30K miles and didn't have any spark plug problems...my 07 Jeep Hemi has them too and so far so good (29K miles). I have Champions in all my yard equipment and no problems there either...but I have heard those stories too....just never experenced it myself....