As I was cruising along I suddenly lost power.My 1990 model 140hp Evinrude could not go over 2000 revs.As I tried to accelerate past 2000 revs the motor would die down.I have no trouble in starting the motor,it starts up fine but it will not go over 2000 revs and it sounds like it is missing when i accelerate.What might be the problem?Any replies greatly appreciated please.Thanks