I take it, your talking abotu a spark "ping" or "knock" .

does it run good at wide open throttle? and does it idle well? I'm
sure you're running fresh gas in it. Old fuel will cause spark knock,
but will usually run crappy regardless of RPM, that is, if you can get
it started. You might also consider having the spark timing checked to
see if it hasn't slipped.


I don't think you have a stator problem, that is, unless the battery is
draining and isn't being charged.



nig.xl wrote:
Hi
I have a 6 year old merc 50 that starts to knock every so often,
possibly as if it's firing on only 2 cylinders. Anyone know of any
common faults to look at first ? I'm thinking possibly one of the coils
maybe or are stators a problem with this engine. Also it only seems to
happen at mid range so maybe a carb issue ? Anyway I'm open to
suggestions.