RPM Drops and back to normal

[cep022]

I was out the weekend before last and at cruising speed I noticed the port side engine the RPM would "bog down" and come back to normal several times. Almost like one of the cylinders was not firing correctly.
After stopping and checking the clean out plug and all that was fine. After that everything seemed fine.
This past weekend it pretty much did the same thing. No issues at idle at all.
I ended up changing the plugs out and then ran some and did not have it happen again during that time. But then like I said it was interment when it was doing it.

I've attached pictures of the plugs that I pulled out. Does anyone see anything on them that looks like it was the issue ? Other then the use of too much anti seize on the threads?
2010 SX240

 

[RobbieO]

I was out the weekend before last and at cruising speed I noticed the port side engine the RPM would "bog down" and come back to normal several times. Almost like one of the cylinders was not firing correctly.
After stopping and checking the clean out plug and all that was fine. After that everything seemed fine.
This past weekend it pretty much did the same thing. No issues at idle at all.
I ended up changing the plugs out and then ran some and did not have it happen again during that time. But then like I said it was interment when it was doing it.

I've attached pictures of the plugs that I pulled out. Does anyone see anything on them that looks like it was the issue ? Other then the use of too much anti seize on the threads?
2010 SX240

You can use an ohm meter to check the internal resistance if you are trying to isolate a bad plug. Problem is they may all show good because they are not hot and underload.

 

[cep022]

I checked and they all tested fine. Guess will find out truly next outing under normal conditions if the spark plug change took care of the issue.