2005 3.0L Alpha One Spark Plug Torque

[2005185LX]

Hello group.

What is the correct torque for the spark plugs on this engine? The Mercury documentation that came with my boat (2005 185LX Stingray) does not say what the torque spec is. I called Mercury and they say 22 ft-lbs, however, I found this page from NGK:

http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp

I am using the recommended plug ACMR43LTS, which are 14mm, with no gasket (conical seat). This engine has a cast iron head, so according to NGK the torque should be 10.8 - 18 ft-lbs. My torque wrench only goes up to about 19 ft-lbs, so I'll need to get a new wrench if I tighten them as much as Mercury recommends. Doesn't 22 ft-lbs sound too tight?

Thanks

 

[Alumarine]

I just tighten them snug and a bit and that's it.
Never had one come loose. I also use never seize but some don't like it.

 

[Fun Times]

Hi there, welcome to iboats!

If you're not comfortable setting the torque of the spark plugs by feel (calibrated elbow = no torque wrench) then it's time for a new torque wrench as the correct spec for this engine model is 22 ft-lbs. If it helps you any, I'll just add that even Volvo Penta says 22 ft-lbs in their manuals for the same spark plug numbers and engine years as yours.

https://www.perfprotech.com/blog/articles/mercruiser-30l-mechanical-specifications#

 

[Bondo]

Ayuh,.... Welcome Aboard,.... I too, go to Snug, 'n atad more,....

 

[Watermann]

Same here snugged up with a 3/8" ratchet and I use a small amount of anti-sieze on the threads as well. Never had a plug come close to being loose yet.

 

[2005185LX]

Thanks for the responses.
I contacted AC Delco because I think 22 ft-lbs is too high despite what Mercury says, and here is their response:

Thank you for visiting the ACDelco website.

In regards to your inquiry on the torque for your spark plugs AC-MR43LTS, our research shows we list 17-15 feet pounds for this plug since it is a tapered seat, if it was a gasket seat we would recommend 26-29 feet pounds.

We hope this is the information that you are looking for.

For further assistance, you can contact our experts at the ACDelco support center by dialing 1-800-ACDELCO (223-3526).


Regards,

ACDelco Internet Response Team

So, I'm going to torque mine to 17 ft-lbs and see what happens.
By the way, after fogging my engine last fall, I discovered that one of the plugs had broken in half. Perhaps this was caused by over torquing?

 

[81 Checkmate]

Id say the plug that was broken was caused by someone trying to torque a spark plug. Have you ever tried to remove a spark plug that some idiot tighten down to much. It's a drag. Cut up knuckles, cussing and so on. In my many years never heard of anyone torque a spark plug...... Just snug them up and tweek it a tad more.

Sorry for venting!

 

[bruceb58]

My Volvo manual says 20. I always use a torque wrench when tightening, especially spark plugs.

If I had a mechanic that didn't use one on everything he did, I would find another mechanic.