1978 Johnson 2HP outboards Service Manual, Page 29Get this manual
Figure 4-5Ground Wire and Armature Plate Screw
Figure 4-6Armature Plate Removed
Figure 4-7Liner Boss and Groove
CLEANING, INSPECTION AND REPAIR
SPARK PLUGS Inspect plug for cracked porcelain and worn electrodes Clean or replace spark plugAdjust gap to the specified .030 inch (0.8 mm)In re-gapping, adjust only the ground electrode, as attempting to bend the center electrode will crack the insulatorSee Figure 4-8Poor motor performance and premature spark plug failure may result from improper spark plug installationBefore installing the plug, be sure the plug seat in the cylinder head is clean and free from obstructionsSee Figure 4-9Install new spark plug gasket, screw the plug in by hand, then tighten to the specified17-12 to 20-12 foot pounds (24 to 27 Nm)
If threads are stripped in cylinder head, Heli-coil inserts are available