1971 Johnson 4HP Outboard Motors Service Manual, Page 28Get this manual
RUBBER INSULATOR
Twist leads counterclockwise spark p1ugs and remove high tension 1ead anchorSee Figure 4-3Disconnect throttle lever to armature linkSee insert, Figure 4-3dUnscrew flywhee1 nut, (See Figure 4-4) and three flywhee1 screwsUse an appropriate flywheel ho1ding too1 when removing flywhee1 nutUsing flywheel puller (Special Too1 #378103), flywhee1 from crankshaftSee Figure 4-5Loosen the four head screwsRemove armature p1ate from power headSee Figure 4-6
Figure 4-2Hot and Co1d Plugs p1ugsSpark p1ugs are c1assified according to the temperatures at which they are designed to operate, or COLDSee Figure 4-2Se1ection of the correct spark p1ug depends the type of service to which it is subjectedUn1ess the spark p1ug is proper1y suited to the motor, trouble arise which might interpreted carburetor difficu1tyVery 10w trolling speeds will tend to fou1 plugs due to the not burning from the coreHowever, at fuH throttle with hotter plug, the operating temperature too high, resulting in preignitionextreme temperature range will difficult to control with one plugSpark plugs furnished with the motor are selected for average serviceSpark plugs recommended for the HP Mode1s are: 1Champion: J6J 2Figure 4-4Removing Flywhee1 Nut