1985 johnson 185,preignition problem.

[ciscokid]

Hi guys,havnt been on here in a while.I changed my plugs out today,and one cylinder has what looks like aluminum melted on my plug.Why is just one cylinder doing this? Any suggestions are appreciated,thanks in advance.

 

[fishinwrench]

Let's do a compression check.

 

[Lenard]

I recommend to pull off the head anyway (after compression test), because you need to verify the cause. Big chance you need to rebuild that cylinder/the whole powerhead.