Re: evinrude yachtwin 4 HP slow running adjusment knob ??
If the carb setting has not been interfered with set it in its mid position !
You can try altering it once the engine has warmed up. Turn it clockwise until the engine just starts to falter then back off until it runs evenly again. Pull the knob off and refit it in its mid position .
For the full explanation of setting the mixture see the first section of
http://forums.iboats.com/showthread.php?t=167352
I find with my 6hp that it helps to turn it fully clockwise (to weaken the setting) start on full choke, then turn it fully anticlockwise (enrich the mixture) at the same time as pushing back the choke knob. Then slowly retuning to the mid point as it warms up. But that's me! Once set correctly there should be no need to touch it.