Merc 115 Poor Performance and smoking badly

[Volphin]

This engine is a circa 1986 Merc 115 inline 6, Serial # OB 145105. It's mounted to my Dad's fish & ski. He had it out toward the end of last season, and it just quit and would not restart. He used the trolling motor to get to the dock and I loaded her up. After a cursory (literally and figuratively) inspection, it seemed to have lost spark. Dad took it to a hole in the wall boat guy who replaced the stator with a merc part. It starts now, but is low on power and smokes pretty badly. I just kept her on the trailer, took her to the ramp, lowered the trim and started her up. She started hard and smoked like the dickens. Methinks a spark box has gone south. Opinions?

 

[Chris1956]

Well, it could be bad spark or something else. I would take a compression test and then a spark test. if you have even compression (within 15%), and you have spark on all 6, I would inspect the fuel pump. If the fuel pump diaghram has a hole, raw fuel leaks into the motor causing spark and rough running.