Mercruiser 3.0 LX spark plug failure

[Rake722]

So I have a 3.0 LX and I was 13 miles offshore when the engine lost 500 rpm and a very loud clatter begun. We killed the engine and use the ancillary to get back only to find something that I have never seen in my life before.

The local Marine Engineer installed short reach delco MR43T instead of NGK BPR6EFS long reach plugs.

He only installed one spark plug as the previous one snapped. The rest of the plugs were correct when we were out on the water and the failure happened. We examined the engine and return to Port and found that the ceramic part of the spark plug that he installed had completely separated from the metallic part which was left screwed into the head.

Had the responsibility of four people on my vessel when it failed and I believe that the wrong part was installed and as a result of this we suffered this failure

Can anyone explain how the ceramic section of the spark plug could separate from the metal casing and cause exhaust gases to escape freely from the cylinder explaining the clattering sound? I thought we had thrown a rod it was so loud.

 

[Scott Danforth]

Improperly tight plug will overheat as it can't transfer heat to the head. This results in the ceramic heat fracturing and blowing out

 

[Bondo]

Ayuh,..... What's the vintage/ serial number on the motor,..??

 

[Rake722]

Ayuh,..... What's the vintage/ serial number on the motor,..??

0F268759

Never seen anything like this

 

[Bt Doctur]

its not unuasual

 

[Rake722]

Well short reach plug was used instead of long reach and the part number of the plug was M43T which isn’t specified for this engine so I am guessing that it was a contributing factor to the failure

 

[Rake722]

Well, we were 4 miles off sure when this happens I swear it sounded like the engine had thrown rod. Engine takes longer spark plugs and the local engineer installed short reach plugs which to me means the heat was concentrated in the spark plug hole causing the spark plug casing to overheat and release the ceramic.

 

[Scott06]

Well, we were 4 miles off sure when this happens I swear it sounded like the engine had thrown rod. Engine takes longer spark plugs and the local engineer installed short reach plugs which to me means the heat was concentrated in the spark plug hole causing the spark plug casing to overheat and release the ceramic.

I had a center electrode come out of an NGK plug on a Toyota was rattling around in combustion chamber intermittently tapping.

Like u I thought engine was really messed up, took valve cover off saw nothing amiss, for lack of any other thought took a plug out and saw the center electrode is gone. Put in a new plug let it idle and sound eventually stopped. With a bore scope piston top looked shot blasted, had the car another couple years with no issue