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Propulsion System - Troubleshooting

The information provided is for a 2002 Duffy 18' Classic. Many systems and components are common across models and years.
It is up to you to determine if this information applies to your boat or not.

Safety

• With or without shore power, there is enough electrical energy on your boat to kill you. Do not work beyond your capabilities and take appropriate precautions, such as shutting off all power sources whenever practical.

• Electrical connections in marine environments commonly degrade or fail and are a common source of problems.
  • There is no common ground bus. Grounds often connect to other ground wires, leading to a build-up of resistance and complexity. If you are seeing unusual behaviors that cross systems (e.g. cabin lights stopped working unless navigation lights are on), it may be due to an electrical system finding a new path to ground.
• Mechanical components fail much more frequently than purely electronic components. Check connections, contactors, switches, and potentiometers before assuming a purely electronic component, such as the motor controller, has failed.
• When troubleshooting, keep in mind the fail-safe operation of the motor controller. If the motor controller receives an input it doesn't like, it will shut-down the motor.

• You will need a basic electrical meter in order to troubleshoot problems. Being able to use the basic functions of a meter (such as measuring voltage drop and resistance) will help you tremendously.
• A small wire brush will be useful for cleaning connections. Use brass brushes for brass/bronze connections and stainless steel for others.

Symptom: No response when key switch is turned on

• Common Causes:
• High resistance or failed connection(s)
• Tests
• The key switch is the common distribution point for all systems, so a failure here or before the key switch should be your focus. Check connections from end-to-end. The best way would be to check for voltage drops at each connection point*.

Symptom: Motor periodically stops without a change in throttle setting. Moving the throttle to "Off", then forward/reverse often temporarily resolves the problem.

• Common Causes:
1. Throttle potentiometer has a dead spot or forward/reverse limit switch is failing, causing intermitent communication with the motor controller resulting in the controller failing safe by shutting off the motor.
2. High voltage contactors are not making good contact, intermittently providing low or no power to the motor*.
• Tests
1. When this occurs, the diagnostic LEDs on the Infaspeed box should always match throttle settings. If not, check throttle to motor controller connections and, if OK, Rebuild the throttle.
   The throttle and motor controller electrical system is designed to fail-safe. If there is a loss of signal from the throttle, the motor controller will shut off the motor. The throttle must be returned to neutral before the motor controller will recognize additional throttle signals.
2. If the motor controller diagnostic lights consistently match throttle inputs, one or more contactors may be working intermittently. Inspect contacts with power off*.

Symptom: Motor does not work, performance has degraded in one mode (forward or reverse), or RPM fluctuates.

• Common Causes:
• High voltage contactor failure(s)
• High resistance connection(s)
• Motor issues
• Tests
1. Diagnostic LEDs on the Infaspeed box should correctly represent the key switch and throttle inputs (e.g. on/off, forward/reverse). If not, there is a problem between the throttle, motor controller, or LEDs.
2. You should hear a strong mechanical "clack" from high voltage contactors in the Infaspeed box when you change throttle modes (forward/off/reverse).
   • If you do not hear the contactors in all modes, one or more contactors or their connections are likely bad. The motor controller could, instead, be bad, but this is much less likely.
   • Check for high resistance or voltage drops between connections. You may hear the contactors and measure full voltage, but there may be high resistance between connections which will limit current*.
3. Check for these issues that are common to DC motors.
• Worn brushes
• Brushes not moving freely in their brush holders
• Pitted/burned commutator, which may be caused by poorly mated brushes or excessive wear.

Symptom: Power rapidly degrades while motoring

• Common Causes:
• Batteries
• Poor high voltage connection(s)
• Tests
1. Battery energy gauge on the instrument panel will show low power when boat is at full throttle.
2. Check battery charge and specific gravity.
3. Check high voltage connections by using a meter to find potential voltage drops*.

Symptom: Turning on an accessory (e.g. navigation lights, cabin heater, horn) causes your motor to stop.

• Common Causes:
• If you have a problem with high resistance connections or a failing component, turning on another accessory can expose it. This could cause the motor controller to shut-off the motor as a fail-safe response.
• Tests
• See above information for diagnosing bad inputs to the motor controller.

*Resistance at a poor connection will increase as current passing through the resistance heats the connection, so a relatively small voltage drop when cool can result in a larger drop when under a high current load. This is especially an issue in lower voltage systems.

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