1970 Johnson 1.5 HP Outboard Motor Service Manual, Page 27Get this manual
Figure 4-5Ground Wire and Armature Plate Screw CLEANING, PLUGS
Figure 4-6Armature Plate Removed
Figure 4-7Bushing, Tongue and Groove
AND REPAIR
Inspect plug for cracked porcelain and worn electrodesClean the electrodes with point DO NOT sandblast spark plugsAdjust gap to the specified .030 inchIn re-gapping, adjust only the ground electrode, attempting to bend the center electrode will crack the insulatorSee Figure 4-8Poor motor performance and premature spark plug failure from improper spark plug instal1ationresult Figure 4-8Checking Spark Plug Gap