1978 Johnson 4HP outboards Service Manual, Page 86Get this manual
7075 HP Page 4-6 STEPIgnition coil output check: -Remove high tension leads at spark plugs and connect needle point spark checker to high tension leadsCrank engine with key switch and observe spark(Cranking speed must be at least 350 rpm See Figure 4-11aSpark strong, steady, and firing one coil at time across 1 2" (12 mm) gap, ignition system is okay(Check spark plugs bWeak, erratic, or no spark from one or two ignition coils, go to Step 4cWeak or erratic spark from all three coils, check charge coil input into power pack, Step 3dNo spark from all three coils, check key switch, step 2
Page 4-12
It+INOTE
If any spark is present at spark gap checker during sensor out-
put test, replace power pack1If meter reads 0.3 or higher on to groundIf OK, go to Step 52If meter reads lower than 0.3 ground and sensor resistancefications, low meter reading is sensor magnets in flywheelall sensor leads, check for shorts on any sensor, check for shorts to If sensor resistance meets specicaused by low engine rpm or weak