Hi all, I am new to this, so hoping I post this in the correct place ... My problem is a 2002 Merc 115 4 stroke EFI engine ... This engine happens to be one that they used Yamaha power heads for, so it is often hard to locate parts .. My problem is the top two cylinders carbon up within minutes of running the engine .. The idle is very rough and after a day or two out on the water, the engine starts to misfire .. Replacing plugs will start the process all over . This engine has great compression, uses no oil at all , and wide open throttle mostly is always OK unless plugs too fouled.. I read about FSM or VST modules that might have a split in one of the hoses, but cannot locate anything that resembles what I am seeing .. I should mention Spark is OK .. I replaced the ignition coils, and the fuel injectors .. I have had this in to the shop and spend literally more than the engine is worth .. I am ready to junk it .. Any help would be appreciated.. Thanks
