1970 Johnson 1.5 HP Outboard Motor Service Manual, Page 23Get this manual
3-8 Run engine at ful1 throttleUsing tachometer, adjust high-speed needle until best high-speed setting is obtainedLow-Speed Needle NOTE High-speed needle must correctly adjusted as described efor low -speed needle adjustment is begunWith motor at operating temperaturerun at slow speed (700-750 rpm) with test propeller in tank boat Adjust low-speed knob until highest reacling and smoothest performance are obtainedAllow Adjustment of high15 seconds for motor respond to speed needle MUST repeated after final low-speed needle adjustment Install adjustment knobsDO NOT disturb position of needlePosition knobs so that each boss is pointing straight up and push back to original position needlesWith 650 rpmand needle valves correctly adjusted motor should idle at