Spark Plug problem

[Jmorrell588]

When driving my boat today, I noticed that the motor starting to run rough when I was trolling. It was running fine 5 minutes before. When I gave it more power to see if it would clear it up, it continued to run rough. Even at WOT. I did fear the worse thinking I lost compression. When I got home, I took out the plug in the side that I suspected since I could tell that was the side running bad. The part that you push in and back to get the correct gap was pushed up against the electrode. What might have caused this to happen? Note, I know it was the piston head that tapped it. Wondering if there was a cause and that the plugs have been in the motor for 4 months with no problems.

 

[Joe Reeves]

Re: Spark Plug problem

JMorrell.... The problem isn't the s/plug. Something has let loose within the engine which allowed the piston to travel higher than normal, or something has broken off, traveled to the top of the piston and slammed the plug electrode shut. Time to remove that cylinder head and do an inspection.

 

[Jmorrell588]

Re: Spark Plug problem

Mr. Reeves thank you for your input. Might I ask if I am able to take a look at this part since I have a spare head of this Motor. It is a 90hp 1989 Evinrude VRO. Actually it is the old head that I asked to keep when they put a new one on it a year ago. Do I need to take the fly wheel off or can I go in from the back of the cylinder by taking each plate off and take a look in there. Like I said, since I have a spare that has not yet been rebuilt. Mr. Reeves or anyone who might read this, have any input.

 

[Jmorrell588]

Re: Spark Plug problem

Bump

 

[BillP]

Re: Spark Plug problem

That is an odd situtation. Like already posted, take the head off and check. With that said I would also examine the other cyls too. If really bad the piston top will look like it was shot peened...same for inside of head. The cyl walls will be scuffed big time if the ring let go. You can probably get an idea of how bad by looking through the plug hole. If all looks well inside look for a loose rod or aluminum deposits on the plug electrode. Bent plug electrodes are rare unless a bad plug installation.<br /><br />Bill P.<br />40+ yrs running OMCs (worth at least 2 cents)