Spark plug story

[firstlight]

Good day all....I have a 1998 Honda 90 with almost 600 hours. Strange situation has developed this year......I installed new plugs and after running about an hour or so (I use the boat as a commuter and usually run around 4800 rpm) the #2 cylinder died. Upon removal of the plug, the electrode gap was completely closed and totally black. I figured I must have bent it upon installation so put another one in it's place. Same thing happened. Yesterday, not knowing what to do (and sitting 8 miles out) I doubled up on the washer and installed another plug. Looked at it when I got home and it seemed fine. Any theories as to the cause of this? I initially thought the piston was carboned up and hitting the plug but figured it wouldn't run for an hour if that was the case. Could one cylinder be running hot and softening the electrode enough to bend?? A little jittery about taking her out at this point.

 

[WillyBWright]

Re: Spark plug story

Double check the plug numbers. There is probably a sticker that tells what to use on the motor. Either you're using an extended tip version of what is called for, or you have a loose rod bearing.

 

[firstlight]

Re: Spark plug story

I spoke to a mechanic last night who put the plug under a magnifying glass (duh!)and you could see where the electode and plug bottom was dinged up. His opinion is that something is or was flying around in the combustion chamber. He said if the ignition temps got hot enough to melt the electrode the piston would have been on it's way to the dump by now. Tonight I'll try a magnet, vacuum and pulling the plug and blowing whatever is in there out. Oh yeah, I might add in a few Hail Marys while I'm at it...gonna be a beautiful weekend. Thanks for the responses.