Spark Plug Seperation

Has anyone ever had a spark plug separate on them while running?

I took the family to the local swimming hole on Monday. On the way home we were running about 3/4 throttle when I heard a loud bang and a hissing sound in time with the engine rpm's. I shut the motor down to investigate (thinking I blew up my motor) and found a plug wire just hanging solo. A minute later I found the porcelain insert part of a spark plug in the bilge. The metal threaded part and cathode were still in the head, but the center porcelain part got spit out. It was the strangest thing I've ever seen.

We limped the rest of the way home not knowing how much damage there was to the engine.

Once home I pulled the threaded part out and inspected it. It was in perfect shape except for missing the porcelain center. I replaced the plug and the motor fired and ran well. I've also since replaced the other 7. I was just curious if this may be an indication of some deeper issue that may need attention before I do blow it up or if it's was likely just a bum plug.

The motor is a mercruiser 260 that I rebuilt in 2011. Had zero issues til this. The spark plug was a Champion RV8C. I changed to Bosch plugs, hoping it was just a faulty plug issue.

Any thoughts/ideas?

Re: Spark Plug Seperation

The spark plug was a Champion RV8C.

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Figures......
I've seen it happen several times with champion plugs. One of the reasons I have such a strange dislike for them. They might be ok for a lawn mower, but they have no place on a boat.

Stick with the AC or NGK plugs that Merc recommends and save yourself some problems.

Re: Spark Plug Seperation

My dad told me similar, that's why I changed to Bosch. Hoping the higher price will equate into a better quality plug. Funny though, I never thought about having spare plugs onboard with an I/O. I now have 7 spares. LOL

Re: Spark Plug Seperation

Overkill82k5 said:

My dad told me similar, that's why I changed to Bosch. Hoping the higher price will equate into a better quality plug. Funny though, I never thought about having spare plugs onboard with an I/O. I now have 7 spares. LOL

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Nope,.... yer draggin' 'round 7 more junk Champ spark plugs,....

Re: Spark Plug Seperation

Bond-o said:

Nope,.... yer draggin' 'round 7 more junk Champ spark plugs,....

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i have had the same thing happen a few years ago on my suv.it too is why i dont like champion plugs,that and the fact they seem to change heat range on there own. so it is ngk,autolite,or bosch for me.

Re: Spark Plug Seperation

Same thing happened to me on my Crownline LPX the FIRST time I went out with it....lol...mine blew out because the plug was actually rusted. The shoulder blew off and the only thing left in the motor was the threaded area. Had to have the dealership pull it out. They changed all the plugs and been fine after that. I did have it towed in afterwards though. Didnt run it to the dock like that.

Re: Spark Plug Seperation

It's possible to crack spark plugs while installing, but It might have just failed too. i use NGK plugs, never a problem.

Re: Spark Plug Seperation

Bond-o said:

Nope,.... yer draggin' 'round 7 more junk Champ spark plugs,....

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LOL, figures. I will have to stop again and pick up some real ones. Great, now I have 15 emergency spares... haha. Anyone need a spare?

Thanks a bunch for the info. I'm sure most of you know, or can imagine, that state of panic that consumes you when something unexpected and seemingly catastrophic happens when you're out on the water... All I kept thinking was "I just rebuilt this dang motor from the ground up, what could I have missed". It is such a relief (in a way) that inferior plugs were to blame. Now I can quit beating myself up mentally. Thinking the new motor was toast made for a rough afternoon. I'm still surprised that happened, as I have never even heard of that, before it happened to me. Live n learn I suppose...

Re: Spark Plug Seperation

NHGuy said:

It's possible to crack spark plugs while installing, but It might have just failed too. i use NGK plugs, never a problem.

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That I have heard of and seen, but I have both halves of the plug and they are both 100% intact, just separated. I will be picking up some NGK's before the next outing.