Motor Issue HELP!

I have a 1998 triton with a 175 Johnson ficht on it. Has been a good engine since the beginning. Last year had a new stater put on it but that has been the only problem. Had it out this weekend and it started making a very rough noise when you put the throttle just past the idle position but no where near plane position. It still had power and got up on plane and ran top end fine. It was just that fast idle area it was rough sounding. My buddy mentioned a fuel pump, but I was hoping someone else my have some ideas. HELP PLEASE!!!