Differences

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--- tin_boat [2026/08/05 16:31] – created donald
+++ tin_boat [2026/08/05 20:20] (current) – donald
@@ Line 4: / Line 4: @@
   * Spark plugs are Champion QL77JC4 or NGK BPR7HS. Gap: 0.030"
-J10RCOM
+===== J10RCOM =====
 <code>Johnson Model: J10RC0M (or J10RCOM)
 Year Determination
-The model J10RC0M / J10RCOM does not follow the cleanest form of the standard INTRODUCES year code, which makes an exact year slightly less straightforward.
+The model J10RC0M / J10RCOM does not follow the cleanest form of the standard INTRODUCES year code,
+which makes an exact year slightly less straightforward.
 However, based on very similar models in the Johnson parts catalogs (especially J10RC series):
@@ Line 19: / Line 21: @@
 </code>
+===== Testing the coil =====
+<code>
+Outboard Ignition Coil Testing
+(For Johnson / Evinrude 9.9–15 HP and similar 2-stroke motors)
+You can test the ignition coils with a basic digital multimeter (ohmmeter). Here’s the practical procedure.
+Tools Needed
+Digital multimeter set to Ohms (Ω)
+Spark plug wire pliers or needle-nose pliers
+Clean rag
+Safety First
+Disconnect the battery (if equipped) or remove the spark plug wires.
+Make sure the engine is not running and the kill switch is in the OFF position.
+. Primary Winding Test (Low Resistance)
+Disconnect the small primary wire(s) from the coil (usually a single spade terminal).
+Set the multimeter to a low ohms scale (200 Ω or auto-ranging).
+Touch one probe to the primary terminal.
+Touch the other probe to a good engine ground (or the coil’s metal mounting tab/core).
+Expected reading (typical for these motors):
+.1 – 1.5 ohms** (most common range is 0.5 – 1.0 Ω)
+Reading of 0 or very close to 0 → shorted primary → bad coil
+Reading of OL (infinite) → open primary → bad coil
+. Secondary Winding Test (High Resistance)
+Keep the primary wire disconnected.
+Set the multimeter to a higher ohms scale (20kΩ / 20,000 Ω).
+Place one probe on the primary terminal.
+Place the other probe inside the spark plug boot (touching the metal terminal).
+Expected reading:
+,000 – 8,000 ohms** (3k – 8k Ω) is common on many older Johnson coils
+Some models fall in the 225 – 350 ohms range (especially later CD ignition coils)
+Outside this range or OL → bad secondary winding → replace the coil
+. Short-to-Ground Test
+One probe on the primary terminal
+Other probe on the metal core/laminations of the coil
+Should show OL (no continuity). Any reading means the coil is shorted to ground.
+Quick Tips for Your Motor
+On 9.9/10 HP Johnsons of this era, the coils are usually mounted under the flywheel on the magneto plate.
+Always test both coils (most of these motors have two).
+A coil can pass the resistance test and still be weak under load. The best final check is a spark tester
+(in-line or gap-style) while cranking.
+Would you like the typical resistance values specifically for the charge coil / stator as well
+(common cause of no-spark on these motors)?
+</code>