Spark plugs for 2010 4.3 Merc?

[Mikaman]

Bought a new SeaRay last year, with the 4.3L 190 HP Mercruiser V-6 engine. It is NOT fuel-injected, it has a carburetor with "TKS" (Turn Key Start). I keep the boat at my summer cottage, about 300 miles from home. I bought the boat from a SeaRay dealer near home, but I have it serviced at the marina on the lake where I use it. That marina is a Mercruiser approved service facility, but not a SeaRay dealer.

The marina (service manager AND their lead mechanic) tells me that the engine requires Iridium spark plugs. They base this on two things: 1) the boat was delivered from the factory with Iridium plugs (they saw this the very first time they removed the spark plugs from my boat -- no one else had touched the boat prior); and 2) the technical data sticker mounted on the engine itself has a line for spark plugs, and it lists an Iridium type part number. I checked this sticker, and they are correct, it says "Spark Plug: AC41-101" which is in fact an Iridium plug (although strangely, this is an automotive spark plug number, not a marine spark plug).

The dealer (service manager and one of their mechanics) tells me that the engine does NOT require Iridium plugs. They base this on three things: 1) they say that only the fuel-injected engines require Iridium; the carbureted version does not; 2) they looked it up in their Mercruiser (or maybe SeaRay?) on-line parts book, by year/make/model AND by my boat's serial number, and the part number for spark plugs is the standard type plug, not Iridium; 3) they double checked to see if there were any Service Bulletins for my boat that superceded the parts book, and there were no Service Bulletins regarding spark plugs -- hence the parts book is still correct.

According to the dealer, the correct spark plug is AC Delco MR43LTS, which is a marine-grade platinum plug. The Mercruiser part number is 33-862029.

I asked the dealer why the boat had Iridium plugs as delivered by the factory, if Iridiium is not required. They said that new boats often come through this way from the factory, it is OK to use the Iridium plugs even though they are not required, so the factory sometimes installs Iridium perhaps because that's what they had on hand when this engine was assembled. I have not yet asked the dealer why the technical data sticker on the engine lists the Iridium plug.

The iridium plugs cost about 3 times as much as the platinum plugs. WHO IS RIGHT?

Also -- less important but I am curious -- why is the Iridium plug an automotive plug, not a marine-grade plug? Are all Iridium plugs inherently "marine grade", without being any different from the automotive version?

Thanks for any advice/help.

 

[Fun Times]

Re: Spark plugs for 2010 4.3 Merc?

Someone over looked this Service Bulletin, This should help clear the air a little bit.

http://ww2.justanswer.com/uploads/ROCKETBOAT/2008-12-09_042519_SPARK.pdf

They now have a newer plug number since this Service Bulletin came out though, And it looks like you have the new number (AC-41-101).

If in doubt, it's always best to use the info that is on top of the engine flame arrestor cover/sticker.

We would need your engine serial number to comment on what plug you could use in your engine safely.

Also if the engine is a 2010, it would seem too soon to need new plugs? unless you are having a problem? Engine hours?

 

[Mikaman]

Re: Spark plugs for 2010 4.3 Merc?

Thanks FunTimes ... I will try to get someone to callme with the s/n of the engine (I'm not at the lake right now).

The way I read this Service Bulletin, the correct replacement plug is MR43LTS, which is not iridium. I'm curious why "they now have a newer plug number ... AC 41-101" which is definitely an iridium plug.

THe reason we need new plugs -- according to the marina that services the boat -- they (marina) highly recommend replacing spark plugs every spring, because (they claim) fogging the motor in the fall to winterize it normally results in fouled plugs. They claim that most of the time, the plugs will clear themselves when the boat is started in the spring, but not always, and to be "on the safe side" they always replace sparkplugs every spring. I told them I am confident I would notice if one or more plugs were fouled & misfiring, but they claim that it can be hard to tell if only one is misfiring and most of their customers wouldn't realize it, and further engine damage can result from operating the engine for extended periods with a fouled plug (raw fuel washes down cylinder wall, diluting oil, and maybe ruining piston rings). Frankly, this sounds like a scare tactic to me, or a PYA thing where they just don't want anyone to possibly come back & complain of a misfire after they pick up their boat in the spring.

However, they also claim that they lake-test our boat every spring, after the oil change & tune-up ... so it seems to me that if they left the old plugs in there, and one or more didn't clear, their highly trained & experienced Mercruiser technicians would immediately notice the fouled plug. If the boat runs fine (no misfire) during their lake test, I can't see how a spark plug could somehow become fouled later on from remnants of the fogging oil.

But honestly -- if the MR43LTS plugs are correct for my engine, I'd be perfectly happy to have a new set installed every spring. I just don't want to pay for six new iridium plugs every year, that seems excessive.

 

[jmarty10]

Re: Spark plugs for 2010 4.3 Merc?

I have the same engine and haven't changed the plugs in 3 years. Fires right up every time. Your mechanics are definitley getting you on tune ups. If youre not firing on all cylinders you will notice performance issues right away. My old boat only fired 3 out of 4 cylinders, couldnt plane out at all. Changed plugs and engine ran like a top. I think the newer type plugs have a much longer life than some of the older ones.

 

[achris]

Re: Spark plugs for 2010 4.3 Merc?

I had the iridium plugs die after 3 years (200 hours). In Australia they are $26 each! So I had some platinum plugs shipped over from USA, at about $4 each. I have been running them since and have had no problems. The iridium plugs are advertised to last 10 years... I also run a fuel flow meter and am very preceptive to performance changes. The platinum plugs show no difference to the iridium plugs in my engine.

Chris........
P.S. the only difference between 'marine' and 'automotive' plugs is the price..

 

[Mikaman]

Re: Spark plugs for 2010 4.3 Merc?

Hi FunTimes, I got the serial number, it is 1A613172 Any further advice? Thanks for your help.

Mikaman

 

[Fun Times]

Re: Spark plugs for 2010 4.3 Merc?

Hi FunTimes, I got the serial number, it is 1A613172 Any further advice? Thanks for your help.

Mikaman

Hi Mikaman, I certainly can understand your dealer wanting to change out spark plugs every year after fogging a engine, To them as a servicing dealer it's more about trying their best at keeping a good name instead of wanting a bad name out there, To them it's most likely not a gamble their willing to make over (in your particular case about $30.00ish dollars in parts) Because if your engine did develop a engine miss due to bad plugs next year you would not be a happy boater, Then usually the not so happy customers would end up telling 10+ people of the low quality work they have done by not putting new plugs in your engine after fogging it, Then of course unfortunately there is always the happy customers who only tell 2 or 3 people they like this service shop because they do a good quality job at trying to make you happy in the end by putting in new plugs every year, Just so that you don't need to wait 2 + weeks next year just to figure out you need new plugs due to their bad work from last year.

Well you're in luck, The plugs you could now be using is Mercruiser part number 33-862029 which = AC-MR43LTS with a MSRP of $5.00 each.

The way I read this Service Bulletin, the correct replacement plug is MR43LTS, which is not iridium.

Even with you're newer engine model you are correct.

I'm curious why "they now have a newer plug number ... AC 41-101" which is definitely an iridium plug.

I believe (theorizing) the new plug numbers is to help compensate for some of the newer emission control engines they now have out, along with it seemed like AC-delco was starting to discontinue some of the older plug numbers you seen in the Service Bulletin.

Also just so that you're aware of the fact, Your engine serial number has a very important Service Bulletin (Bulletin No. 2010-11R1) that may need to be addressed still by a Mercruiser dealer, And it appears that Mercruiser may not have been able to get of hold of you at that time. Have one of your dealers run your engine history.

08/28/2010 FIX CAMP INTERMED SHIFT CABLE SB : 4-2010-011 NO FWD ADDRESS

 

[rick3452]

Re: Spark plugs for 2010 4.3 Merc?

AC-MR43LTS with a MSRP of $5.00

I picked up these plugs at NAPA for $2.00 per plug....

Best of luck....Rick

 

[koutroul]

Re: Spark plugs for 2010 4.3 Merc?

Hello I have a 2007 4.3 TKS (190hp). Engine serial number: 1A053879.
Should I use iridium plugs? What is the model of plugs that I should use?

 

[Bondo]

Re: Spark plugs for 2010 4.3 Merc?

Hello I have a 2007 4.3 TKS (190hp). Engine serial number: 1A053879.
Should I use iridium plugs? What is the model of plugs that I should use?

Ayuh,.... AC-MR43LTS will run just fine in yer motor....

Btw,.... Welcome Aboard,...
In the future, post a thread of yer own, insteada hy-jackin' 1 of these old 1s...