Mercruiser Spark plugs

[Up1225]

I am confused about the spark plugs for my mercruiser 3.0lx. On the engine label it calls for an Ac-MR43TS. In the book it says AC-MR43T. I can’t find that the 43TS is actually a plug... anyway. The plugs that were in the boat were RS12YC. It seems to me that if the MR43T’s are right, that the piston should have been hitting the ones I want to replace, the RS12YCs... Any help would be appreciated

 

[Up1225]

Plug on left came out of engine, on right is the MR43T

 

[Fun Times]

The cover info is incorrect to show your spark plugs to be MR43TS....It is missing the L...It should read MR43LTS from AC-Delco.... It's just a misprint from new...They had a few misprints like that back then.

A good alternative would be NGK BPR6EFS or should be Merc part number 33-816336Q if you can't locate an original AC MR43LTS plug.

RS12YC is a equivalent part number to both numbers and safe to use in your engine model.... It's just usually a less desirable plug to use in the marine world is all.

https://forums.iboats.com/forum/engi...lx-spark-plugs

https://www.perfprotech.com/mercury-...00?umodel=9549

http://www.sparkplug-crossreference....DELCO/MR43LTS/

Just reread some more of your post....Looks like someone installed the correct long reach plug that's used in the LX engine model of your year time frame.... The non LX engine would use MR43T like in your hand...That is why you're seeing a difference.....Don't install the short plug MR43T in your hand as it is incorrect for your engine 3.0LX model with that ignition system / head design. Item # 20, https://www.perfprotech.com/mercury-...00?umodel=9549

 

[Up1225]

Thank you!