Re: Johnson 35HP outboard motor 1950-60
The easiest way is simply to do a continuity check, as follows:
(Regular Magneto Coils - Continuity Test)
(J. Reeves)
Checking the continuity of the ignition coils....... Have the ohm meter set to High Ohms.
Remove the primary wire from points. Remove the coil ground wire. You do not want either of these wires touching anything.
Connect the black lead of a ohm meter to the spark plug boot terminal, then with the red ohm meter lead, touch the ground wire of the coil.
Then touch (still with the red lead) the primary wire. You should get a reading on both touches (contacts). If not, check the spring terminal inside the rubber boots of the spark plug wire.
If there is no continuity between the secondary circuit (spark plug) wire and the primary or ground, remove the coil from the armature plate, then check the continuity directly between the prong within the coil (prong that the plug wire connects to) and the primary and ground. Poor or no continuity of a coil (or plug wire) is one reason for weak spark, s/plug fouling, or no spark.
And of course, if the coil is cracked, discard it regardless of whatever reading you may obtain.
Switching it with a known firing coil is a sure fire way of testing it. If it does not fire in its original location but fires in another location, then obviously the coil is okay and the problem is elsewhere.
