2003 Merc 4 stroke 15hp stalling

[erniegator1]

My 15hp 4 stroke is stalling just past idol. it doesn't shut down as long as I throttle past the "dead" spot. If I increase the throttle a little bit at a time, just about 1/4 turn past idol it starts to act funny an wants to stall kind of like a cold motor would if you give it too much gas before proper warm up. I use my boat 2-3 times a week for the last 2 1/2 years without any problems and I want to get her back into good running condition.
I think its carb related but have never worked on this motor.
any suggestions on where to start?
I just changed all the fluids and plugs and its still doing it.
thanks