Piston hitting spark plug

[snert21]

I have a 84 Evinrude XP100 V4.<br />Mod: E100STLCEM Ser: R 08160584<br /><br />When I checked the spark plugs after a day out, One of the plugs had its gap completely closed.<br /><br />So I replaced it and tried again with a new plug, and again it closed.<br /><br />I am assuming the piston is coming up hitting the plug, but when turning the flywheel by hand and watching the pistons it doesn't seem to be coming up any higher than the rest.<br /><br />I want to make sure I am using the right plugs. Does anyone know what is recommended for my engine? Or does anyone know what may be the problem?

 

[Terry H]

Re: Piston hitting spark plug

What spark plug are you using and have you de-carbed this motor lately...just a Thought

 

[DJ]

Re: Piston hitting spark plug

snert21,<br /><br />I had this happen to an old 3 cylinder looper. It wasn't good news. <br /><br />It could be as simple as carbon, but I kind of doubt it. <br /><br />You have lost or are losing a bearing (needle) at the crank or wrist pin.

 

[snert21]

Re: Piston hitting spark plug

I had Autolite 2634. At the moment it has NGK B9HS10.

 

[snert21]

Re: Piston hitting spark plug

I took the cover off and it looks like a big chunk of metal somehow broke off the piston.<br />It has seriously beat up the piston and the cover.<br /><br />Guess that is as far as I can go. Will take it to the shop.