HELP Spark Plugs for 72 mercruiser 140 DONT FIT

[Ryanlewis2010]

Hi guys im trying to find some plugs for my engine a 72-75 mercruiser 140 the manual says to use mr43t, it currently has RN14YC by champion. I am not sure if this is why i have a bogging problem in my boat under load is really bad it feels just like it did in my car when i had bad plugs. any problem using these as i will be getting the right ones in a lil bit i feel these are the problem because its not hot enough to burn the excess fuel when accelerating this is the last thing i can think of let me know please.

What are you using?

Ryan

 

[Don S]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

Junk the champions, put in the correct plugs and see how it runs and go from there.
I have fixed a lot of issues over the years by getting rid of those sorry champion plugs.

 

[Ryanlewis2010]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

ok so ill go with the ac delco plugs hopefully thats it i think the heat range is to low

 

[cr2k]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

+1 on junking the champions. They are for OMC outboards.

 

[Ryanlewis2010]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

Hey guys quick problem i got the mr43t plugs today AND THERE TWO SHORT the block that was in here takes them as a plug but the spark plug holes on this are different an suggestions please help b4 the store closes thanks

 

[Don S]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

If the seat is not tapered in the head, you need the AC CR-44N spark plug.
How long are the treads in the head?

 

[Ryanlewis2010]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

the ones i pulled out of the running motor are about 1in and the ones that are supposed to be in there and out of the other head are about .5in here is a pic

 

[Don S]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

That's because the head on your engine is 20+ years newer than 72.
You need either the AC MR43LTS or the NGK BPR6EFS

Now that we know this, what other things are not 1972 on this engine ?????? Might have a lot to do with the bogging.

 

[Ryanlewis2010]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

thats wierd but it fits the the old 75 manifold

 

[Ryanlewis2010]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

will this SP-447 motorcraft plug work its cross refrenced to be a replacement for the ngk version?

 

[Ryanlewis2010]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

or this ngk is cross referenced to the ac delco PN 2238

 

[Don S]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

If you would quit cross referencing and get what is supposed to be in there, it might work right.

The long reach plugs should have a tapered seat in the head, does it?????

 

[Ryanlewis2010]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

Yes it did i found the right plug surprisingly advance auto had the right mr34tls IN Stock so its in and oooo baby is there a big difference in the way she purrs. once i fine tune the idle that thing should be perfect (knock on fiberglass) Thanks don. Still curious on how the whole 20 year newer head still fits the original manifold is this like a vortex head (if they made won for a four banger). would be intersting to hear more about this.

Thanks

Ryan

p.s. the whole cross refence thing is cuz i really want this thing to run so i was being impatient which is all apart of being a teenager haha thanks for your patience

 

[fat fanny]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

Man I have to agree with Don A/C for GM, Autolite & Motor craft for Ford and the rest for whats left period!!! you will see the difference in performance.

 

[Ryanlewis2010]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

I see as above but i get what your saying we were typing at the same time

 

[Don S]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

p.s. the whole cross refence thing is cuz i really want this thing to run so i was being impatient which is all apart of being a teenager haha thanks for your patience

Ahhh yes, "the hurrier I go, the behinder I get" syndrome.

The manifolds will bolt to different heads, just slightly different port sizes. Things all have to work together to work correctly.

 

[Ryanlewis2010]

Re: Spark Plugs for 72 mercruiser 140

Re: Spark Plugs for 72 mercruiser 140

Ahhh yes, "the hurrier I go, the behinder I get" syndrome.

Funny never heard that before well im about to go out on the water test the new setup out ill reply with the details

thanks ryan