Yamaha EX: Overheat Warning, Then Limp Mode: Cavitation or Sensor?

A question that often comes up for the EX: short rides work, on a longer tour the overheat warning comes and then limp mode. M-JET DIAGNOSTIC helps separate cooling and sensor.

What you watch

• Engine temperature (15) and exhaust manifold water temperature (65) over ride time
• Thermo switch in the switch status
• Engine speed during water change or cavitation
• Fault memory for active temperature codes

Cavitation or sensor?

If cooling water is missing, for example due to cavitation or foreign objects in the inlet, the temperature values rise plausibly. A defective sensor, by contrast, often shows jumps or impossible values. It is also reported in forums that the problem hardly shows in calm conditions and only occurs on longer tours. The recording makes the difference visible, and you replace nothing on a hunch. On real overheating, shut off. According to the EX manual, overheat and oil pressure warnings reduce engine speed automatically; as a remedy it names cleaning the intake and letting the engine cool.

Related topics

• Yamaha EX Beeps While Riding: Oil Pressure, Temperature or Battery?
• Yamaha EX Won't Start: Check Voltage, Relays and Cylinders
• Yamaha WaveRunner Overheating and Temperature Sensor
• Diagnostics and fault codes for your Yamaha model
• All Yamaha WaveRunner diagnostics topics

Everything runs via app over Bluetooth, for Yamaha WaveRunners from model year 2002 to today. Learn more about the M-JET DIAGNOSTIC for Yamaha WaveRunner.