I have a 2004 Yamaha 60HP 4-stroke that suddenly won't run past 4700 rpm. At 135 hours, all scheduled services done, clean fuel filter and good flow to the filter. It runs nice and smooth, no snorting or hesitation, just won't get beyond 4700 rpm. It also has developed a flat spot between 3000 and 3500 rpm. Does this sound like a carbon buildup problem? I seldom run it beyond 4000 rpm, maybe that contributed to the situation. Any thoughts? thanks in advance.
