350 Magnum Running Rough at 1100-1300rpm

[bnicov]

My buddy has a 19ft Donzi with a 350 mag in it. It runs rough at 1100 to about 1300rpm but smooth at idle and at higher rpms. The carb was just rebuilt, new plugs, wires, cap, rotor and timing checked. Anybody have any ideas??

 

[guyjg]

It runs rough at 1100 to about 1300rpm but smooth at idle and at higher rpms. The carb was just rebuilt...

Does it happen when you throttle up? Will the engine smooth out if you hold it at that RPM range? Was an OEM carb kit used?

 

[bnicov]

I'm not sure what type of carb kit was used. The problem was present before the rebuild and tune up and is still there. The problem is there only in that rpm range and goes away while throttling up. But, at that range, it is constant and does not go away.

 

[guyjg]

Disconnect the tach. and see if the engine still runs rough. Tachs. can cause the problem.