5.0 Mercruiser TKS.
A few days ago I developed a misfire in my motor. I couldn't remember the last time I changed plugs so I bought spark plugs distributor cap and rotor. I began pulling plugs. They looked normally worn until I got the # 5 plug out. I should have posted a pic, but this plug looked brand new. Shining electrode and pure white insulator. Now it's impossible that this plug was not firing for multiple seasons. I got nervous and did a compression test to that side of the motor. All seems good compression 130-135 in all cylinders. I checked for water intrusion in #5 and found none. I replaced all plugs and found a crack in the distributor cap. Replaced it started motor and runs great. Took a ride under load and runs great.
Can anyone explain the condition of the #5 spark plug?
A few days ago I developed a misfire in my motor. I couldn't remember the last time I changed plugs so I bought spark plugs distributor cap and rotor. I began pulling plugs. They looked normally worn until I got the # 5 plug out. I should have posted a pic, but this plug looked brand new. Shining electrode and pure white insulator. Now it's impossible that this plug was not firing for multiple seasons. I got nervous and did a compression test to that side of the motor. All seems good compression 130-135 in all cylinders. I checked for water intrusion in #5 and found none. I replaced all plugs and found a crack in the distributor cap. Replaced it started motor and runs great. Took a ride under load and runs great.
Can anyone explain the condition of the #5 spark plug?