93 Evinrude 115 V4 bent plug electrode

[chopperguy]

So, after replacing almost all ignition components she was running great until Sunday. During a 12 mile trip home on the ICW at 4500 RPM, she suddenly droped RPMs by 500. I limped the thing home. She was shuttering every so often like a. Miss fire. Got her out of the water. Check the plugs. The left bank plugs were wet and the top plug had a bent electrode, see photo. Compression check was 90 psi on both cylinders. Same as when I bought the boat. Anyone ever see this happen? I am not sure how to proceed. Should I pull the head and inspect the piston? Compression is good and everything seems to be moving properly.

 

[pepper]

looks like to me piston came up to far and hit plug ,could be slack in rod bearing or wrist pin. hope you geter fixed.

 

[boobie]

Something could have went through the motor with the compression you have or you have a bearing going out.

 

[chopperguy]

Do you think this warrants an engine teardown or change the plug and try running it again?

 

[racerone]

Step # 1 is to remove cylinder heads and inspect.----Sounds like broken rings to me.

 

[Bosunsmate]

Move the piston to top dead centre and then with a soft rag on a screwdriver press on the piston through the spark plug hole.
See how much play you get compared to the other cylinders.
It may take you a while to get the knack of it but you will get a feel for the amount of play each piston has. If that top one has more play than the others then suspect big end or wrist pins. You can also do this test at bottom dead centre

 

[emdsapmgr]

If the piston lost the upper ring, parts of the ring may have become wedged between the piston crown and the plug tip while the engine was running. There is some reason you dropped 500 rpm's suddenly. Agree, pull the head. Have a look.