All,
I posted a thread a few days ago about my 2014 250 Proxs having a miss at higher rpm and overall not having the power it used to. Well, last night when replacing the plugs, I pulled this one out. Obviously there is supposed to be a gap. My question is, what would cause this? Did the mechanic over tighten when installing or is this a mechanical issue?
Things that I would consider:
Are all six the same plug
Has the lack of power been since plug change
Improper gaping technique
Dropped plug on hard surface before install
Overflexed.weakened side electrode
Im not a mechanic, just adding my thoughts
That motor should have been running bad ALL the time, not just at higher RPM!
Overtightening will not cause that issue. How did the boat run when that plug was FIRST installed? I would look in that cylinder with a borescope, before running the motor again.
The plug was installed a year Ago. Honestly I dont run the boat hard so, never really noticed a problem. But did notice the holeshot was lacking. Look20190421_094157.jpged at the top of the plug and there is no sign of impact. 20190421_094120.jpg
Also, I checked the gap on the other 5 plugs and they were correctly gapped. With no signs of impact on the head of the plug, I'm thinking it was a faulty plug. There is low chance the mechanic would have installed the plug like this.
Ground electrodes were bent during or after removal, due to the appearance of the porcelain there had to a gap to be colored that wayOriginally Posted by AaronWKU
Pict 2 on post 4 indicates the plug was not removed straight out of the hole, probably caused by not enough clearance around the socket during removal. Got to go straight in and out or this will ocur
Last edited by lpugh; 04-21-2019 at 11:21 AM.
Thank You Leon Pugh
This picture was taken immediately after removal. Not sure how pressure could have been applied to the electrode upon removal.
Aaron I can sure that plug was firing properly when it was installed. Look closely at the side of the ground electrode and you will see where it make contact with, probably the threads in the head as it was removed causing it to bend closing the gap and throwing the iridium contact out of alignment. I suspect this was one of the plugs that is difficult to get a straight shot at with the socket and side pressure was applied during removal after unthreading it. It is a good idea to get all the connectors and hose out of the way for this job as well as removal of the lower cowls. I would not recommend reusing that plug. Be carful gapping them, use only a wire gauge and be sure the positive and negative electrodes align correctly. You can see if you look closely the small iridium contact area on the ground electrode, it must be in alignment. Do not use a plug socket to start the plugs, use a piece of rubber hose that slides snugly over the porcelain area. Be sure to use dielectric grease on the area that the plug wire connects to, you want to seal out moisture intrusion and eliminate carbon tracking down the side of the plug. Be sure your socket is perfectly clean as a dirty socket will transfer contaminates and cause carbon tracking
Thank You Leon Pugh
IMHO that looks like the plug was dropped, picked up and installed without looking at the tip. Possible it was damaged like that in the box but who installs plugs without checking the gap? There's really no such thing as a pre-gapped plug, and the nonsense about "you can't gap an iridium plug" is one of many internet myths. You don't gap 'em like we used to gap the old styles of plugs, but you definitely can check and re-gap when needed. No way to screw that plug in far enough to contact the top of the piston unless you are a heartbeat away from a motor failure where one end of the connecting rod has a lot of slop. Not very likely. I would conclude installation error, fix it and move on. Certainly will kill power.
2008 Bass Cat Pantera Classic
2014 Mercury Pro XS 200
I agree with Leon.....This plug was firing properly at some point in its life.....then something happened to the electrode.
I agree that it looks like the plug was firing correctly at some point. I just was curious as to how it could have eneded up in the condition.
I found this when Installing new plugs. I was never planning on reusing. Thanks all for the comments. Hopefully she runs like a scalded dog now!
Could have swallowed something that went into that cylinder. I would not run the motor again without looking in that cylinder with a bore scope.
Savage makes a good point. I had an old 2.5 that swallowed a reed retaining screw 25 years ago. Only hint was missing on that cylinder. Since this was a racing motor, and it was not very hard to do, I pulled the head on general principles, and ended up replacing the piston and sleeve. Screw even left an impression in the head but I left that alone with no issues. Sure played hell with top of piston, the plug, and the exhaust port however. Better to find such problems before they detonate into a major repair.
2008 Bass Cat Pantera Classic
2014 Mercury Pro XS 200
Can the arm warp under certain conditions? Perhaps if bent too many times, the arm becomes weak and curls under high heat? Just a thought.
I looked at the piston through the plug hole and all was smooth with no scarring. I have no idea how this happened. I find it very hard to believe the electrode was bent upon removal though.
Aaron, the motor has not ran on that plug since the gap was closed up, leaving only the fact that it happened during or after removal. If you want to test this, place a plug in the hole with the ground electrode on your right and as you pull it back out pull the plug to the left such as will happen on removal in tight quarters. The evidence is on your picture in post 4. It takes very little pressure applied to the side of the electrode to cause this. I have seen this many time on long reach plugs, it can happen on installation as well, in your case it did not
Last edited by lpugh; 04-23-2019 at 11:24 AM.
Thank You Leon Pugh
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