Cough, burp and sputter

[ralpht]

my 1986 johnson 25 hp motor burps and seems to mis-fire below 1800 rpms. the carb has been cleaned and the motor serviced professionally twice. the motor runs great above 2000 rpms but is hard starting and rough at idle and slow speeds. I have new fuel w/ additives, plugs and wires. any clues with carb or ignition?

 

[racerone]

Have you checked the operation of the manual primer ( takes the place of a choke ) for the starting problem ??-------------Is the carburetor properly synchronized with the ignition ??-------------Poor idle like that is often the result of the carburetor opening too early and the low speed / idle circuit does not work properly.

 

[ralpht]

my motor has a key operated choke/primer that functions OK. My mechanic said the carb and ignition were in synch when they tuned the engine in Nov 2011. I will re-check with them.

 

[racerone]

Have them check compression too.-----The thermostat is in place and working as designed ???-------You could hook up a timing light and see if it is an ignition miss or something else !