2000 merc tuneup

[merc6]

what are the gaps on the current plugs? that could also be an issue.

[Johnnyiroc]

If it is running rough and you are going to remove the plugs, I would do a compression test of all cylinders, guage is like $30. This may save you the expense of plugs, coils to only find out your head gasket is leaking or a valve isnt sealing right....feels just like a misfire.