2001 225 ox66 cylinder not firing

[mickybrun]

Hi, this is my first post. I have 2 2001 225 Ox66 and one of them cylinder #4 is not firing. WOT rpm is short 400-500 rpm. This engine's rpm goes even with the other one except at wot? VST filters are new, lp fuel pumps are new, O2 sensor is clean. All the plugs look the same except this one, it was completely covered in oil. I'm thinking its a coil but I'm open to ideas.

Thanks in advance.

 

[99yam40]

compression and spark are easy to test,
have you done any testing?

 

[mickybrun]

Tomorrow I'm taking compression. I put the spark plug to ground and it has spark. I've read that sometimes the coils get weak. What about the injectors?

Here's a pic of the spark plug in that cylinder: