MERCURY 496 MUFFLED POP OUT OF EXHAUST

[Ontothenext1]

My '05 496 MAG makes a muffled pop noise on the port exhaust when idling. I have no loss of power (I don't think) and it doesn't run rough but, it does leave a weird residue on my port side swim step (Exhaust exits right above swim step). Anyone else have this issue or thoughts of where it could be coming from? It makes NO popping noise when I give it gas, ONLY when in neutral and idling.

 

[Riverryder]

sounds like a failed gasket?

 

[Shlbyntro]

perform a compression test and fuel pressure test. pay careful attention to how the individual spark plugs look.

you could very well be dealing with a failed fuel injector and/or related valve issues.