A number of motor faults may occur while the IRB is in operation. These include:
- Fuel blockages
- Faulty fuel hoses
- Loose electrical connections
- Water in fuel cell
- Air in fuel cell
- Spark plugs
You will learn how to diagnose and rectify these basic faults in your training and during the course of normal operations.
Slow running
A well-tuned motor should tick over slowly in neutral and in gear. Continual low-speed running will oil up the spark plugs and the motor will start to miss. Give the motor a short burst at high speed to burn excess oil off the plug points. This aspect should be given particular attention if the IRB is stationary for prolonged periods, such as will occur when performing water safety duties. If a slow running motor is not rectified after the short burst, it should be noted in the I.R.B log, the motor should be tagged, and the appropriate officer notified to arrange a motor service.
Propeller slip
Propeller slip occurs when the rubber bush is loosened and is characterised by the motor over-revving and the IRB moving forward in a jerky motion.
Propeller slip is caused by the propeller hitting a rock or sandbank. The initial shock is absorbed by the rubber bush. Continual shocks loosen the rubber bush and finally the propeller will tend to slip.
Once a propeller shows signs of slipping it should be immediately inspected and serviced. Propellers must be re-bushed by an outboard motor service agent. Propeller slip can be minimised by getting into the habit of stopping the motor before moving into shallow water and tilting the motor inboard on approaching the beach after stopping the motor.
Motor overheating
Motor overheating may be caused:
- when the water pump impeller is worn
- when the motor thermostat is jammed
- when there are blockages in water intakes, or anywhere in the water jacket
- when towing
- when dry starting the motor
A blocked intake (e.g., by a plastic bag or seaweed) can cause overheating. To check the cooling system operation, run the motor in a test tank and observe if water is being pumped out of the ‘tell-tale’ water outlet. If there is no water discharge or steam, immediately stop the motor.
Immediate referral to a marine motor mechanic or technician will be required.