Hi,
I have a 2004 Mercury 50 HP 2-stroke. I have it on a 16 ft aluminum boat. It has a 4 blade 11 pitch prop. Top speed was 38 mph @5500 rpm. Now it will only due 30 mph and it will go no higher than 5000 rpm. Does anyone have any idea what has happened? It starts great and idles and runs fine...