05 15HP Mercury 4 Stroke idles OK but runs rough

lelievre12

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Dec 1, 2013
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I have overhauled the carby and idle is very good but as soon as I try and rev, the engine starts to surge and develops no power. I have tried choke on and off, no difference. New plugs, no better. I have double checked that the main nozzle and jet are clean and float needle looks OK. I am suspecting the CDI or coil but am not sure these would be bad if the idle is so smooth. Any others have this problem with the Merc 4 stroke?
See Video here-
 
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