Chrysler 20 and 30 HP Outboard Motors Service Manual OB 3435, Page 46Get this manual
4Find lean setting as follows :
Idle StopManual Start1Adjust idle speed screw until engine idles at 750 RPM in forward gearFigure 13
ASlowly turn carburetor idle adjustment screw clockwise 1 turn, wait 10 seconds
Adjust throttle to keep engine from exceeding 900 RPM Keep turning screw 118 turn at time and pausing 10 seconds until tachometer shows that engine speed has peaked and is decreasingEngine will begin to pop when too lean BNote position of screw slot (lean position) and return screw to original position 5Find rich setting as followsASlowly turn idle adjustment screw counterclockwise (1turn with 10 second pauses) until engine begins to roll and gallop from the rich fuel setting BNote position of screw slot (rich position) 6Set idle adjustment screw at midway point between lean and rich settings Figure 12
Figure 13Adjusting Idle Speed (Manual Start)