Hi, I have a problem with my mercury 115 HP in line six, running wide open at 4100 rpm's for several minutes then I hear and see the rpm's run up to 5000 rpm's.<br /> The speed shows about 40 at 4100 rpm's with throddle wide open, and speed about 46 at 5000 rpm's. It idles great at 1100 rpm's and runs great. I had the carbs rebuilt, fuel pump and water pump rebuilt. A friend told me it sounded like one of the control boxes was dropping a cylinder and then picking it back up. Do you think this could be the problem? If so how do i check to see which one of the two control boxes it is?<br /> Thanks, Walter