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Mercury 9.9 to 15 HP issues

T

Trailtech

New member
Hello this is my first post. I bought both a mercury 9.9 2 stroke long shaft and had all the parts to make it into a 15 HP short shaft. After assembly and adding both the 15 HP carb and exhaust tube, the Engine does what seems like a lean sneeze but there are no air leaks and the main jet is a .072. I don't know what the issue is . The engine ran great before and the carburetor is basically new. I have tried everything and am at a loss. The 9.9s ignition pack looks different from the 15 HP I am taking the parts from but I think it may be jetting that is the problem. Any advice would be great thanks
 
What year is your 9.9 motor. The 9.9 was built on 2 different blocks depending on the yr, a 10 cid and a 15 cid block. The conversion only works on the 15 cid block
 
So for anyone wondering, they increased the displacement in 1995. I rebuilt the carburetor and changed the plugs so hopefully that somehow helps although I am doubtful. Is there a way to post videos on here? I will film it tomorrow when I run it and maybe seeing is better than reading about it. It sounds to me like it is a lean sneeze but the low speed needle adjustment does little to help and it already had the largest jet they came with. The parts motor/carburetor are from a long shaft (2000 15 HP EL) and I am converting a 9.9 short shaft to 15 HP short shaft. Sorry for coming across as a green horn but I am mostly familiar with johnson/evinrude.
 
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