fuel system help
 

I am having fuel problems with my 502zz,can someone point me in the right direction?The boat is a welcraft prima it weighs 10000lbs and has one motor.It has a holley 850vac sec carb I would like to know what jetting I should start with and also,would a to small of a flame arrester cause fuel distribution problems?The engine only has one of those cheap aluminium 6x3 arresters on it.It seems that number 4 & 6 are always one the leaner side when I check the plugs.I plane one buying a 14x3 K&N flame arrester, is this a good choice? THank You for your input . Lorne