3.0L is launching ceramic out of plug, help!

[rebelchem]

I have an '06 Bayliner 175 with a 3.0L mercruiser alpha one. Newly rebuilt carb. Twice, the inner part of the spark plug has been shot out from the same cylinder. The threaded metal stays put, all of the inner ceramic leaves, forcefully. The image shows the setup in that cylinder and the results.

The engine seems to be running fine for a bit and then there is a pinging noise for less than a minute, and then a gun shot sound. When I opened the engine compartment, I saw the electrode still attached to the burning wire on the floor.

Tense moment, but it worked out. Thanks in advance for any help, you and your knowledge are greatly appreciated.

https://photos.app.goo.gl/anbAmk1zijWEQyY87

 

[Scott06]

What do your other plugs look like ? You mention a pinging prior to this happening I would think that is detonation which would be damaging more than just this plug. I think you will find lean running conditions and flecks of aluminum from the pistons on the spark plugs

are they the right plugs the current heat range ?

 

[nola mike]

I think I see parts of your piston on that plug ground strap. Agree with above, sounds like serious pre detonation. Blowing your plug out instead of a hole in your piston/tuliped valves is the equivalent of blowing out a "freeze plug" and not cracking your block. You need to check your timing, fuel, and fuel delivery. You also need to check your compression.

 

[Scott Danforth]

what is your temperature. normally plugs fail when they get really hot.

also, detonation or "pinging" is your motor eating itself. that means your timing is way off and you may be running lean.

 

[TunaFish389]

I would get better plugs. They should hold up to thousands of psi, even detonation shouldn't blow the plugs like that.. Defiently looks like plug defect/ poor quality. I would also double check timing just in case.

The pinging noise is more than likey the plug starting to fail and getting slight blow by till shotgun complete failure...

 

[Furbird]

Is that a spark plug non-fouler in that picture? If those are in your engine, you've got more problems than just a plug going to the stratosphere. Ceramic only pops out if it's a bad plug (this has happened twice on the same cylinder so the odds of that are almost impossible) or something is impacting the end of the plug (either the plug is too long or something is inside the engine that is impacting the end of the plug) and breaking it off. But if it has non-foulers in the engine that is a band-aid for a much bigger issue.