I have a 1998 Mercury 115 2 stroke and I took it out and it would only rev up to 2500 rpm so I took the carbs off and gave them a good cleaning. After putting the carbs back on and taking the boat out again it ran great and would rev all the way up and get on plane fine. After about five minutes of driving at 4000 rpm the motor started to cut out and bog for a few seconds every minute or so and then go back to normal and this continued for the next hour. Any idea what I should start looking at?

