Platinum Spark Plug Upgrade for Mercruiser 3.0

[mwnitz]

The OEM spark plugs for my engine are AC-MR43LTS. I was having a problem in June of 2008 with low idle. It wouldn't stay running without me constantly giving it an extra little drink of fuel. So I replaced the spark plugs and problem solved. I wanted to use platinum. The only thing the parts store could cross reference to was a Champion Platinum Power spark plug # 3401. I gapped them to .045.

I found this technical service bulletin from Mercruiser: http://ww2.justanswer.com/uploads/ROCKETBOAT/2008-12-09_042519_SPARK.pdf
They want that gap to be .045, and it seems that they dont recommend platinum plugs as the gap comes .060. They are concerned of the possibility of techs not regapping to the proper gap!?!?! Seems like a ridiculous restriction due to a few forgetful people, but what do I know.

Bottom line: I want to use a platinum spark plug in this motor. What else could I use other that Champion? I would like to change the plugs every 2 years. There's only 4 of them and it's good insurance. It never sees salt water either.

My engine's S/N: OW330527; family 5M9XM03.02VC; MAR 2005.

Thanks!

-MW

 

[Bifflefan]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Plugs are designed for a set gap. if you have to regap them from .60 to .45 then you have the wrong ones in it. At most they will be a couple thousanths out right out of the box.

 

[BeaufortTJustice]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

You might get away with gapping non-platinum plugs...but gapping platinum ones will most likely result in damaging the extremely thin layer of platinum plating on the tip. Once that layer is breached, the extra money you spent on them becomes pointless. Happy boating.

 

[Don S]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

You DO NOT gap platinum plugs. You gently check them, but you do not adjust them. They come pregapped and if too close, then they are damaged and should be returned.
If you look at that service bulletin, it recommends an AC spark plug for your engine, not a champion. The NGK equivalent is a BPR6EFS, not a platinum, but works great in those motors.
There isn't a Mercruiser recommended platinum plug for your engine.

 

[kend301]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

You DO NOT gap platinum plugs. You gently check them, but you do not adjust them. They come pregapped and if too close, then they are damaged and should be returned.
If you look at that service bulletin, it recommends an AC spark plug for your engine, not a champion. The NGK equivalent is a BPR6EFS, not a platinum, but works great in those motors.
There isn't a Mercruiser recommended platinum plug for your engine.

GREAT advice ...LISTEN to this man , platinums rarely work well for extended periods in a system designed for copper plugs and you could do some serious engine damage by running the wrong plug !!

 

[zbnutcase]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Platinum plugs have no place in a marine engine, and personally I wouldn't use Champion plugs in my lawnmower. The NGK plugs have been great for me, thats all I install. 'nutcase

 

[mwnitz]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Roger! I'm sold. I will install a set of NGKs.

You guys are always an abundance of good information. Much appreciated.

 

[JustJason]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Platinum plugs have no place in a marine engine

Carefull with that statement nutcase.... Platinums are OEM in a few motors.

 

[xxxflhrci]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Been running platinums in my 3.0 for the past 13 years with no problems....the same set. If I remember correctly, they are Autolites.

 

[83Evinrude]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Platinum plugs have no place in a marine engine,

Why shouldn't Platinum plugs be used in a marine engine?

My 2004 Volvo 5.0L-GL came with factory installed AC 41-932 Platinum plugs, (some red paint on them). When I bought the boat this summer it was still running fine, but I replaced them with the newer AC 41-993 version of the same plug.

Volvo lists the spark plug gap at .060 for both Carb and MPI V6 and V8 Engines in my owners and service manual. MerCruiser according to the link above, lists the Carb V6 and V8 engines at .045 and the MPI versions at .060, is there a big difference in ignition systems or just manufacturer preference?

 

[zbnutcase]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

You are correct, justjason, however I was referring to old-school carbed engines, should have made myself clearer. 'nutcase

 

[PiratePast40]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

You are correct, justjason, however I was referring to old-school carbed engines, should have made myself clearer. 'nutcase

OK - I'll bite - why not?

Edit - just to clarify, I'm not trying to be a smart alec. I really want to know why a certain type isn't recommended for an older engine.

 

[xxxflhrci]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Is an 1985 with a carb and points ignition old school?

 

[TilliamWe]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Is an 1985 with a carb and points ignition old school?

That's so "old school" it's a "one room schoolhouse!"

 

[Bondo]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Ayuh,... Up until the newer EFI stuff,... The AC Delco, MR43T worked Just Fine for 40 years...
There's No extra fuel mileage,...
No extra power,...
No extra Nothing to be gained from all these Super Sparkplugs...
Just Twice the Price....

And the fact that many Boaters are so anal about puttering on their barge,..
Changing the sparkplugs every spring,.. Most don't have 50hrs. on 'em...

Why O Why spend Twice the money when they'll be thrown away before they're used up,..??

Sparkplug threads are like Oil threads,....

That's why I've been chuckling as I see this thread bouncing off the top,...
The title of the thread,... "Platinum Spark Plug Upgrade for Mercruiser 3.0"....
Somebody tell me,..... What's the Upgrade,..??..?? Sparkplug Dealer Profit maybe,..??

 

[Don S]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

What's the Upgrade,..??..?? Sparkplug Dealer Profit maybe,..??

On a dyno under perfect conditions, there is a .004% increase in power output. Which means you go from 130 hp, to 130.005 hp. If that's not worth an extra 20 bucks for 4 spark plugs, what is.

 

[Bondo]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

On a dyno under perfect conditions, there is a .004% increase in power output.

Ayuh,... I Doubt it.....

The boat goes Faster,... Because of a Lighter Wallet.....

 

[CheapboatKev]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Ayuh,... I Doubt it.....

The boat goes Faster,... Because of a Lighter Wallet.....

Oh man..lol..
I should hit at least 50 on the GPS then...

 

[mcleaves]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

On a dyno under perfect conditions, there is a .004% increase in power output. Which means you go from 130 hp, to 130.005 hp. If that's not worth an extra 20 bucks for 4 spark plugs, what is.

Cool stats Don!! Can you tell me what set of Platinums I need for my OMC 5.0 EFI Ford?? I am looking for a cheap way to get some HP so I can turn those D6's!

 

[PiratePast40]

Re: Platinum Spark Plug Upgrade for Mercruiser 3.0

Just to help answer some questions in my own mind, I did a google search for "why use platinum spark plugs".

Here's one of the links: http://www.accessconnect.com/platinum.htm
Yes, the quotes are from a plug manufacturer but gives some insight as to why the harder metal can be an advantage in the automotive world with modern higher energy ignitions.

It helps explain why some of the wiser ones are saying what they are.