Spark Plugs

[deerfield]

My '07 325 EFI Outback has 160 hours on the engine. The dealer tells me that plugs should be replaced every other year. The service shop is selling them over the counter for $12.95 each. That's like $100 for a set of eight. When I balked at the cost I was told they are iridium and replace the AC plug recommended in my Moomba manual.

Do I need to replace plugs very other year?
Is it worth replacig my current set with iridium?
Why is iridium expensive?
What will it do for me?

Thanks.

[badasshybrid]

I would not put AC plugs back in it. Get you some NGK plugs from O'Reilly Auto Parts. The reg plain jane plugs are around 2.00 to 2.50 each. The NGK Iridium plugs are around 7.00 each. The 2.00 plugs are just fine for the boat thats what I run in mine.

[viking]

deerfield,
I was searching for the OEM plugs as well and near as I can find these have replaced them?

http://www.summitracing.com/parts/ACF-41-993/

[deafgoose]

Spark plugs on cars dont get changed until you hit 100,000 miles.

Why would they need to be replaced so often in a boat that uses the same engine?

I just finished my 3rd season and I am still on the original plugs. It fires up faster than my car when I turn the key.

[deerfield]

deerfield,
I was searching for the OEM plugs as well and near as I can find these have replaced them?

http://www.summitracing.com/parts/ACF-41-993/

viking - The one you located here is platinum. The person working the parts counter at the Skiers Choice dealership said iridium is a step up, replacing platinum. Now, I don't know enough about engines to take on a parts person at a certified shop telling me that iridium plugs are the correct application for my '07 Outback and it'll cost me $100. But it seems that I used to be able to get a good plug for a couple of bucks. Then platinum came along at twice the price. Now iridium comes along at four times the price. No one can seem to tell me the difference other than iridium is better than platinum which is better than regular. Better for my boat or the person marketing spark plugs? I dunno. - Deerfield

[maxpower220]

Spark plugs on cars dont get changed until you hit 100,000 miles.

Why would they need to be replaced so often in a boat that uses the same engine?

I just finished my 3rd season and I am still on the original plugs. It fires up faster than my car when I turn the key.

+1

First, is there any thing wrong with the way your boat engine is running to warrant a change of the plugs? Have you pulled the plugs to inspect them? Visually, you can determine a lot about the way your engine is performing. A web search can give you pictures of plugs running fine, rich, lean, etc.

When I winterize, I pull the plugs to fog the cylinders. I do my inspection then. On my MC that I owned for 7 years, I changed the plugs once. That was due to the fact that I accidentally cracked two of them on a re-install and the boat was not running properly.

BTW, my buddies with Mercruisers are also advised to change plugs every year, so it is not an Indmar thing. You should do what you feel comfortable with, but I get full use out of the plugs and wires until I change them.

[Engine Nut]

Here is the scoop on spark plugs. If you have a 5.7L engine that has catylitic converter exhaust (2007 or newer Assault 340) use the platinum (AC 41-932) or iridium plugs (AC 41-101). If the engine does not have catalytic converters, use the standard plugs (AC MR43LTS).

Spark plugs in a marine engine typically have a shorter life span than in a car or truck because marine engines typically run colder and with richer fuel mixtures than automotive engines do.

The engines without catalytic converters run cooler and richer than the engines with catalytic converters and really do not benefit from using the more expensive platinum or iridium plugs. Save a few bucks and use the standard plugs.

The catalytic converter engines run warmer (but still not as warm as automobile engines) and significantly leaner than the non catalyst engines and the platinum or iridium plugs like those conditions.

[deerfield]

The engines without catalytic converters run cooler and richer than the engines with catalytic converters and really do not benefit from using the more expensive platinum or iridium plugs. Save a few bucks and use the standard plugs.

Engine Nut - I appreciate your guidance. Since my '07 Outback is equipped with the 5.7 325 EFI non catalytic engine I will use the standard plug when it is time to replace. Thanks! - Deerfield

[DOCDRS]

here are the plugs http://www.summitracing.com/parts/ACF-41-101/
http://www.summitracing.com/parts/ACF-MR43LTS/

[MartinCaron]

Those are pictures of my current winterization... What do you think of the old spark plug ?? hehe


https://forum.moomba.com/picture.php?albumid=314&pictureid=3031



https://forum.moomba.com/picture.php?albumid=314&pictureid=3032


https://forum.moomba.com/picture.php?albumid=314&pictureid=3033

[DOCDRS]

plug looks old but ok imo did it come from a forward cylinder on a carbed engine?....nice gapping tool.....looks better than the one i use ,i'm going to get that napa gapper

[MartinCaron]

plug looks old but ok imo did it come from a forward cylinder on a carbed engine?....nice gapping tool.....looks better than the one i use ,i'm going to get that napa gapper


No, it came from a fuel injected 325... not sure of the "forward" thing

[jra007]

No, it came from a fuel injected 325... not sure of the "forward" thing

I think he is referring to the fact that in a carbureted or throttle body injection engine the condition of the plugs always look different from the cylinders at the front of the block as apposed to the ones from the back of the block. In an inboard the front cylinders will run a little leaner because the engine is tilted slightly upward, and even more so when cruzing around. Hence the forward cylinders have to fight with gravity and will look cleaner (since less fuel makes it to those cylinders) and the back cylinders will either be normal or slightly rich. This is not so with EFI since each cylinder has its own fuel source.

[DOCDRS]

I think he is referring to the fact that in a carbureted or throttle body injection engine the condition of the plugs always look different from the cylinders at the front of the block as apposed to the ones from the back of the block. In an inboard the front cylinders will run a little leaner because the engine is tilted slightly upward, and even more so when cruzing around. Hence the forward cylinders have to fight with gravity and will look cleaner (since less fuel makes it to those cylinders) and the back cylinders will either be normal or slightly rich. This is not so with EFI since each cylinder has its own fuel source.

explained very well

[VA LSV]

AC 41-932 platinum was discontinued and replaced by AC 41-101 iridium which are $6.95 at local auto parts stores. Both are actually made by NGK.

I switched to Denso platinum TT in my vehicles but plan on using AC 41-101 in the boat.

[sandm]

I have the 340ext. local schucks/oreilly sold me a set of 8 last year at winterization for around $50. they are a standard plug in the chevy line, and if you get the platinum or iridium, they should come pretty much pre-gapped for the engine.