1981 Johnson/Evinrude 4HP Outboards Service Manual, Page 28Get this manual
bAdvance speed control until mark on cam is centered under rollerSee Figure 3-18 LOW SPEED NEEDLE ADJUSTMENT aWith motor at peration temperatu re, run at slow speed (700-750 rpm) with test propelle in tank or on boatAdju st low speed knob until high est rpm reading and smoothest performance are obtained Allow 30 seconds for motor to respond to adjustmentbPosition low speed knob so that the pOinter is facing down and push back to original position on needle valveWith cam and needle valve correctly adjustedmotor should idle at 600 rpm
FUEL TANK
FUEL MIXTURE motor in excellent mechanical and operating conditionmay give faulty performance because of an improper fuel mixturePetroleum gum and varnish which precipitate from stale ixturemay clog the filter and small orifices th us interfering with starting and normal runningThe use of OMC 2+4 Fuel Conditioner, will prevent and remove gum and varnish For proper fuel mixture, see Section 2Drain and flush tank once every year, tune-up or major repairFlush with clean gasoline or solventRefill the tank with correct fuel mixture