175 hp Johnson poping sound

[JJB]

2000 175 hp johnson carb , I have always been told that a poping sound comes when you are running lean from timming or bad carb adj . I have rebuilt my carbs boat runs good wot but pops at idle or low rpms sometimes . I have adj the carbs like the manual tells you with the boat in the water in gear 650 rpms . I do each carb one at a time until it leans out then back it out slow until the ruff idle stops . its idles good but pops sometimes no matter what I do with these carbs or timming . I also notice my plugs are dirty and wet , the compression is 100 - 110 . thanks for the input jjb