Spark plugs for 2005 Mercruiser magnum 350, Alpha one, so many options ???

[Texasbikers]

Hi, I have a 2005 Mercury Mercruiser 350 magnum I/O with the Aplha one drive, engine serial # 0w320266

I'm super confused on what plugs I need to put in her.
The engine cowl says AC 41-932 and it has AC 41-932's in it, I understand these are discontinued.

The mercury book that came with the engine says use AC 41-983, I was told AC plugs are junk by my mechanic... and to go with NGK...

I looked on Mercuryparts-direct.com and according to the engine serial number it says to use
NGK itr4a15 aka #5599 at Oreilley or Advanced Auto parts, iridium plug

Mercruiser, Mariner, Mercury Outboard Parts, Inboard & Sterndrive Parts Online, OEM Parts Online at MercuryParts-Direct.com

Then I called my mechanic, (my dad, he lives 1,000 miles away), has been a Mercury Master Mechanic for 30 years now, he looked it up by engine serial number and said it shows him,
-NGK TR55ix (#7164 @ Oreilly or Advanced Auto)
-or TR55gp (#3403 @ Oreilly or Advanced Auto)

Anyone know what is the deal with all these variables? I don't mind spending good money on stuff like this, I have the NGK itr4a15 #5599 plugs in hand, any problem using these at .060 gap ?

Thanks
Patrick B in Nashville...

 

[alldodge]

Re: Spark plugs for 2005 Mercruiser magnum 350, Alpha one, so many options ???

Hi, I have a 2005 Mercury Mercruiser 350 magnum I/O with the Aplha one drive, engine serial # 0w320266

I'm super confused on what plugs I need to put in her.
The engine cowl says AC 41-932 and it has AC 41-932's in it, I understand these are discontinued.

The mercury book that came with the engine says use AC 41-983, I was told AC plugs are junk by my mechanic... and to go with NGK...

I looked on Mercuryparts-direct.com and according to the engine serial number it says to use
NGK itr4a15 aka #5599 at Oreilley or Advanced Auto parts, iridium plug

Mercruiser, Mariner, Mercury Outboard Parts, Inboard & Sterndrive Parts Online, OEM Parts Online at MercuryParts-Direct.com

Then I called my mechanic, (my dad, he lives 1,000 miles away), has been a Mercury Master Mechanic for 30 years now, he looked it up by engine serial number and said it shows him,
-NGK TR55ix (#7164 @ Oreilly or Advanced Auto)
-or TR55gp (#3403 @ Oreilly or Advanced Auto)

Anyone know what is the deal with all these variables? I don't mind spending good money on stuff like this, I have the NGK itr4a15 #5599 plugs in hand, any problem using these at .060 gap ?

Thanks
Patrick B in Nashville...

Howdy Patrick
Plugs, there are so many variables and changes with plugs happen. Here is what I would mention and take it for what it's worth, my opinion. You have a 2005 engine and when GM the manufacture, and Mercury the marine modification manufacture decided to use AC 41-932 plugs. So I'm going to say that maybe they knew what their doing. Going to NGK or other plug should be fine (a Ford Chevy thing). My Rinker came out in 1995 with NGK plugs and it ran fine, and in 2013 I replaced the plugs for the first time with AC MR43T. It is still running just fine.

Iridium plugs are very good plugs, my wife's car has had the same plugs in it for 150K miles. If you plan to replace the plugs with Iridum type and never change them again then maybe it will be worth the money. Other wise maybe use the AC or NGK regular plugs and have a great boating season

 

[Texasbikers]

Re: Spark plugs for 2005 Mercruiser magnum 350, Alpha one, so many options ???

Howdy Patrick
Plugs, there are so many variables and changes with plugs happen. Here is what I would mention and take it for what it's worth, my opinion. You have a 2005 engine and when GM the manufacture, and Mercury the marine modification manufacture decided to use AC 41-932 plugs. So I'm going to say that maybe they knew what their doing. Going to NGK or other plug should be fine (a Ford Chevy thing). My Rinker came out in 1995 with NGK plugs and it ran fine, and in 2013 I replaced the plugs for the first time with AC MR43T. It is still running just fine.

Iridium plugs are very good plugs, my wife's car has had the same plugs in it for 150K miles. If you plan to replace the plugs with Iridum type and never change them again then maybe it will be worth the money. Other wise maybe use the AC or NGK regular plugs and have a great boating season

Thanks for the reply. yeah seems spark plugs and what is best is kind of like the what is the best oil discussion :joyous:
I put the NGK Iridium's in that Mercury parts direct had listed, she runs like a champ. And yes, I never want to do that again. With how my engine sits in the boat I had to take exhaust manifolds off to change them and even with drift pin bolts to help those buggers are hard to get back on and HEAVY!!!!

Thanks much!
Patrick

 

[alldodge]

Re: Spark plugs for 2005 Mercruiser magnum 350, Alpha one, so many options ???

I like the way the cast iron manifolds last, but like you hate working with them.... To dang Heavy for this old guy

 

[Bt Doctur]

Re: Spark plugs for 2005 Mercruiser magnum 350, Alpha one, so many options ???

you do not have to remove the manifolds in most cases, what you need to do is grind away the rear of the socket to clear the bottom of the manifolds