OUTBOARDS IGNITION

IN THIS SECTION, YOU WILL FIND THE FOLLOWING SUBSECTIONS:

TROUBLESHOOTING THE OUTBOARD IGNITION SYSTEM
CHECKING STOP CIRCUITS AND IGNITION KEY SWITCHES
TESTING OUTBOARD ELECTRONIC IGNITION COMPONENTS
ADJUSTING AND CHECKING THE OUTBOARD IGNITION SYSTEM
ADJUSTING OUTBOARD IGNITION TIMING

TROUBLESHOOTING THE OUTBOARD IGNITION SYSTEM

Two basic types outboard engine ignition problems:

1)No spark, weak spark, or intermittent spark
2)Improper spark timing

If ignition system fails to produce spark, or if spark too weak to properly ignite mixture, problem exists in one or more components of ignition system. Improper timing results from improper adjustment of throttle synchronization linkage or improper ignition timing. First step when troubleshooting ignition system to give visual inspection, by following these steps:

1)Check system for loose connections, broken or corroded wires, worn or damaged parts, damaged insulation, dampness, or oil soaked wiring.
2)Examine spark plugs and replace as necessary. Make sure each plug gapped to correct specification.
3)Inspect and clean spark plug wires, paying particular attention to the terminal connections at the plugs and ignition coils.
4)If engine contains points, remove flywheel and examine points and condenser(s). Check condenser mounts and connections, and tighten if necessary. Check point gap and compare it to manufacturer’s specification. Recondition and regap or replace points as necessary.

If visual inspection doesn’t reveal problem, check safety interlock switches that engine or watercraft contains. Some outboards use prevent start switches that prevent starting unless gear shift set in neutral. In some small watercraft like jet skis, safety line connects operator to start switch. If operator falls off craft, line pulls key out of switch, stops engine. Test operation any safety devices.

If problem still not identified, need to test ignition system components. Spark test will determine if system producing proper spark. Condensers, coil windings, electronic ignition systems can be tested for shorts to ground or opens with an ohmmeter. Condenser’s output and capacitance and output ignition coil windings can be tested with special coil condenser tester. Output of electronic ignition can be tested with voltmeter.

CHECKING STOP CIRCUITS AND IGNITION KEY SWITCHES

Many outboards equipped with stop buttons or kill circuits. Some larger engines with electric starters also contain ignition switches. These must be checked if ignition system fails to produce proper spark.

In engine with conventional ignition system, kill circuit often just simple grounding switch. When pressed, switch shorts primary circuit to ground. Fault in switch or wiring will cause system to fail to produce spark. Can usually check kill circuits in conventional ignition system visually.

In electronic ignition system, kill circuit also grounds the primary circuit. Usually, only one end of capacitor connected to ground. When stop button pressed, both ends capacitor grounded. Current prevented from reaching, charging the capacitor. To determine if fault present in stop button or kill circuit, need to bypass kill circuit. Procedure used to bypass and check kill circuit of 25 horsepower or 35 horsepower is the following:

1)Separate the three wire connector between the ignition coil and capacitor (power pack).
2)Connect two jumper wires between the capacitor discharge terminals of both ends of the connector. This connects the capacitor to the ignition coils, but bypasses the kill circuit (the third terminal).
3)Connect a spark tester. In a two cylinder engine, connect the tester to both of the spark plug leads.
4)Crank the engine.

If is no spark, or if spark jumps across only one gap of spark tester, kill circuit is okay. If spark jumps both gaps of spark tester, fault present in kill circuit. The stop button and wiring will have to be replaced to correct fault. Tether line type kill circuits can be tested by connecting a jumper wire to the terminals of kill switch receptacle.

An ohmmeter test can be conducted to check ignition circuit in engine equipped with ignition key switch. If ignition switch circuit tests faulty, use ohmmeter to determine whether fault is in switch or wiring. Follow these steps to perform ohmmeter test:

1)Insert the red (positive) ohmmeter lead into the third terminal of the ignition coil end of the three wire connector. Connect the black (negative) ohmmeter lead to ground.
2)Separate the four wire connector between the magneto and the capacitor (power pack), and turn the ignition switch to ON.
3)If the ohmmeter produces a reading of infinite ohms (open circuit), the switch and the wiring are okay. However, if there’s a fault in the switch or switch circuit, the ohmmeter will show a low resistance reading.
4)To isolate the fault, disconnect the stop circuit lead from the switch. If fault is in the switch, the ohmmeter will show reading of infinite ohms (open circuit). If fault is in the wiring, ohmmeter will show a low resistance reading (closed circuit).

TESTING OUTBOARD ELECTRONIC IGNITION COMPONENTS

If results of spark test negative, and you determine that stop button/kill circuit or ignition switch and switch wiring aren’t at fault, other components of ignition system must be tested. Some these tests may be performed with ohmmeter, while others performed with voltmeter.

Ohmmeter set to read low resistance should be used to test sensor or trigger coil for excessive resistance or shorts to ground.. Would separate the four wire connector between the magneto and capacitor (power pack). Then, connect ohmmeter leads between the sensor coil lead terminals of the magneto end of the connector. If ohmmeter shows a reading of 40 ohms, (+/- 10 ohms), the sensor coil is in good condition. If ohmmeter reading doesn’t fall within this range, sensor coil will need to be replaced.

Next, use ohmmeter set to read high resistance to check the sensor coil for a short to ground. Connect red (positive) meter lead to one of the sensor coil terminals of the magneto end of the connector, and connect the black (negative) meter lead to ground. Now observe meter reading. Then, move the red meter lead to the other sensor coil terminal of the connector plug, and observe meter reading. If you note any difference between first reading and second reading, then either the sensor coil or the sensor coil leads are shorted to ground. In this situation, sensor coil must be replaced, or the defective lead repaired or replaced.

Ohmmeter set to read low resistance also used to test the magneto charge coil for resistance and shorts to ground. To check the charge coil resistance, connect ohmmeter leads between the charge coil terminals of the magneto end of the four wire connector. Unless ohmmeter shows a reading of 575 ohms (+/- 75 ohms), the charge coil will need to be replaced.

To check the charge coil for shorts to ground, connect ohmmeter leads between one of the charge coil terminals and ground. If note any fluctuation in reading when the red (positive) lead moved from one charge coil terminal to the other, then charge coil or leads are shorted to ground.

When testing ignition system components, should consult service manual to determine proper test readings. Compare measured values against values listed in service manual to check for problems. Remember that resistance tests should only be performed when engine is cool. If engine hot when you perform resistance test, readings may be inaccurately high. Resistance in an electrical circuit increases as temperature increases.

Next use a voltmeter to test the following components with engine off:

1)The sensor coil output
2)The charge coil output
3)The capacitor (power pack) output

The sensor coil, charge coil, and capacitor may also be tested with engine running. However, this type test requires special testing equipment that enables engine to run with the connector plugs separated. In this type test, the connector ends are plugged into a special adapter, and readings taken from pinholes in the adapter.

Use an ohmmeter to test the primary and secondary windings of ignition coils for resistance and shorts to ground. Can perform these tests with ignition coils on engine. However, must remove ignition coils from engine to test them for high voltage leaks and output power. These tests are performed with a special coil condenser tester.

ADJUSTING AND CHECKING THE OUTBOARD IGNITION SYSTEM

To check ignition system, visually inspect all cables, wires, and connections for breaks, worn or broken insulation, pinched wires, dampness, oiliness, and tightness. Then, remove and replace spark plugs. Be sure that new plugs are type recommended by manufacturer, and make sure that plug gaps adjusted to proper specifications. Also, before installing spark plugs, make sure that spark plug seat clean.

To inspect, adjust, or replace breaker points in outboard engine, will be necessary to remove flywheel. Multicylinder engines will often contain set points for each cylinder. After removing flywheel, visually inspect old points for wear, burning, pitting, other damage. Worn or damaged points should be replaced. If points in satisfactory condition, adjust them to proper point gap recommended in service manual.

Next, before replacing flywheel, inspect crankshaft and flywheel taper for oil traces. Excess oil in either these areas may indicate upper crankshaft seal leaking. After inspection complete, replace flywheel.

No check of ignition system complete until spark test performed. To test for spark, disconnect plug wire from each plug, then connect spark tester to plug wire. Some spark testers allow two or more plug wires to be connected and tested at same time. If tester doesn’t allow this type test, disconnect and ground other plug wires. Grounding wires will prevent arcing or damaging buildup high voltage in ignition system. Set tester’s air gap as specified in service manual. For breaker point ignition systems, air gap usually about ¼ inches. When testing electronic ignition, air gap about ½ inches.

ADJUSTING OUTBOARD IGNITION TIMING

Many small single and two cylinder outboards won’t require ignition timing adjustments. Ignition timing of larger engines should be checked and adjusted with aid timing light. Following procedure describes steps used to check ignition timing in 35 horsepower two cylinder outboard referenced earlier:

1)Disconnect the spark plug wire from the spark plug over Cylinder 1 and connect the timing light to the wire.
2)Run the engine at full throttle.
3)The timing mark should align with the 34 degree mark on the flywheel.

A reading of plus 1 degree or minus 1 degree generally acceptable. If timing off by more than 1 degree, should be adjusted. To adjust timing, stop the engine and turn timing adjustment screws to either advance or retard timing. Then, restart engine and recheck the timing with timing light.

Methods used to check and adjust timing of larger engines may differ, although basic principles the same. Instructions on how to properly adjust timing will be provided in service manual of particular engine.