1992 OMC 3.0L Runs Lean on Front Two Cylinders

[lk2dson]

I have a 1992 OMC 3.0 HO I/O on a 28' pontoon. While servicing the engine I noticed that the front two cylinder spark plugs are almost white. While the back two cylinders are black, almost wet looking. The motor does run. I can't say "perfect" but it's been pretty reliable. It doesn't smoke, and starts up fine.

How does this even happen with a 2barrel Holley carb, and an open intake plenum?

 

[Scott Danforth]

I would do a compression check. More probable that your leaking a small amount of water into the cylinders which is cleaning the chambers