I have a 1996 15 hp Mercury that starts just fine. It also runs great at high speeds. However when trolling it BURPS and sends out a plume of smoke....then runs for a bit and repeats the missing and smoking. The plugs seem to be loading up with carbon at low speed but this never happened before. I need help determining the cause. If I can fix it myself it will save me from getting in line at the local marina for repairs/adjustment. Thanks for an advice.
