One of the carbs on my Mercury 50HP SN:9233460 is having a few problems. I have noticed that the mixture screw on this carb. does not do anything. You can screw it right in or right out and it makes no difference to the running of the engine. I am going to take it to bits this weekend to have a look but does anyone have any ideas as to what this might be so I can concentrate on that area. The carb. does appear to be flooding when in use. The engine cuts out after about 10 mins and then is difficult to use and runs terrible. Does the mixture screw not working give anyone any ideas.<br /><br />Thanks ina dvance.