spark plug issue

[bassboss]

I'm looking for some input or some knowledge from anyone who knows a bit about spark plugs. I had something happen to me I have never seen before. I have a 175 evinrude XP. This past spring I did my usual run the boat a few times to clean out the fogging and winterization fluids. The first time out I could only reach about 4000 rpm, not quite enough to plane out but it was trying. Then, my rpm's came back up like one of the cylinders fired up and I could get up to my 60 mph. Ran fine. This happened again but did not recover. I pulled the spark plugs and found one of them physically could not fire. The ground electrode and the center electrode were touching, like the piston had hit the plug. I purchased 6 new plugs, turned the key fired right up rpm's right up there, idles smooth as could be. Pulled all 6 plugs, fine, not a scratch. ANY IDEAS?

[1javelin]

Was there damage to the plug you pulled?  It sounds like you accidentally collapsed that one plug before you put it in somehow, probably when fogging the inside.  I would consider having a pressure check done just in case.

1jav

[bassboss]

Well, everything checks out fine... I dunno. The only thing that concerns me is these plugs have not come out since last spring and it has always run fine. The only other thing I can think of is a heat issue in the particular plug (had one in my car once) or someone messed with it late last fall and I didn't notice the poor firing. Either way, runs good now.