Purchasing Spark Plugs - Who's & Where

tginz

tginz

New Member
Jan 7, 2008
148
Guilford, CT
Boat Info
2004 240 Sundancer
Engines
5.0 w/ Bravo 3
I replaced the plugs in my 2004 5.0 @ 100 hours and now its time to do it again. Last time I paid $17.89/ ea. at Marine Max...:smt089:smt089:smt089 Recently I found them online through various marine suppliers for as low as $14.75 each.

Question - Are these "marine" MerCruiser plugs the same AC 41-993 plugs I can buy at Napa for 7 bucks? I suspicious that the Marine Max plugs are only just blessed by Mercruiser, the box labelled with Merc #33-884019001, and $10 added to the cost.:smt009:smt009:smt009

Let me know........

tginz
 
NAPA. The experts have said it's the same stuff.
 
Be sure they are platinum tip plugs and they should last more then 100 hrs.!
 
AC doesn't make two different parts with the same part number. Purchase by the plug number from the vendor with the best price.
 
Let's put it this way... We don't even have Merc-brand plugs in stock.
 
Go to NAPA as mentioned. Change them every year to two. There are no special marine plugs.

If you winterize, do NOT mess with iridium. What little coating they have is destroyed with fogging oil.
 
Thanks to all. I'll go for the NAPA for the identical AC plugs.

Didn't want to be "penny-wise and pound foolish" over spark plugs, but also I did not want to be "BOAT-ed" (Bring Out Another, Thousand) either......

Thanks

tginz
 
Wait until you buy a BOAFFT like me. (Break out another F'n Five Thousand.)

Not really, though. After buying it, I had to do some repairs, bought another 3 year warranty, new Strong Seals, Bottom Paint, Amps, Speakers, TV's, Mattresses, Bedding, Canvas, Canvas re-work...
 
dpmulvey said:
Go to NAPA as mentioned. Change them every year to two. There are no special marine plugs.

If you winterize, do NOT mess with iridium. What little coating they have is destroyed with fogging oil.
Click to expand...

The plugs for your engine are most likely AC part number MR43LTS. The M stands for Marine. See the reference chart.

Best regards,
Frank
 
Napa = $9.00 per plug for my motors - 8.1 Changed them last year at 450 hrs and they were over due.
 
For my 8.1s, the AC cross ref is 41-983 (platinums). $20 each from MM or $6 each from Autozone.

I thought the small block platinum plugs were 41-992s/993s, but I might be wrong...Google the Mercruiser part number and you'll find the AC cross references.
 
Last edited:
Mine were due last fall. 350 hrs. on them. RPM surging began first and then later the engine would backfire hard under load at 3ooo rpm. Changed all 16 with the OEM plug. Decided to give our SR shop some money since I have not spent any money with them doing my own service and the boat being so reliable. I have actually spent more on the darn genny having little issues every other year than the mains ...
 
Just an update - I contacted AC customer service regarding my plugs. They do NOT make different plugs for marine applications. Numbers are numbers. I found my 41-993 plugs @ my local NAPA - with a commercial discount they were just over $6. A long way from $17+ @ Marine Max.

Thanks for the help.

tginz
 
I need to replace my plugs as well but I am seeing some confilcting information on what plug to use for the 5.0MPI

A previous poster with the same engine said he is using AC 41-993

Another supplier's link provided below says it is a 41-932
http://www.sterndrives.com/sparkplugs.html


My manual says use AC 41-983

Normally I would trust the manual but I have seen suggestions on 3 different plugs for this engine so am a little confused. Just want to get the right plug! :grin:

Thanks
Jason
 
burwellj78 said:
I need to replace my plugs as well but I am seeing some confilcting information on what plug to use for the 5.0MPI

A previous poster with the same engine said he is using AC 41-993

Another supplier's link provided below says it is a 41-932
http://www.sterndrives.com/sparkplugs.html


My manual says use AC 41-983

Normally I would trust the manual but I have seen suggestions on 3 different plugs for this engine so am a little confused. Just want to get the right plug! :grin:

Thanks
Jason
Click to expand...

Trust the Merc TSB link in my above post

The merc TSB calls for 932's for 05 and earlier and 993's for april of 06 and later. It also goes on to say:

"AC 41-932 spark plugs (P/N 33-884019) will be replaced by AC 41-993 spark plugs (P/ N 33-884019001). The spark plugs are fully interchangeable. Serial number breaks
have not been recorded." So, either plug will work

The same TSB has a statement for the misprint in your manual where it calls for the 983's, (there's even another TSB for the misprint on this TSB) won't hurt your engine but are not the recommended plugs.

"In some owner's manuals, the AC 41-993 (Misprint should read 983) spark plug used in 496 and 8.1L engines was
incorrectly listed as the appropriate spark plug for 4.3 MPI, 5.0 MPI, 350 Mag MPI, and
MX 6.2 MPI engines. The heat range and the thread length of these spark plugs are
correct. The firing tip on the AC 41-983 is longer and extends slightly deeper into the
combustion chamber than the correct AC 41-932 (now being replaced by AC 41-993)
spark plug. While the AC 41-983 is not the recommended spark plug, its use will not
harm the engine or its performance."

Hopefully that clears it up for you
 
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