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  Aural Alarm: Interpretation of Meaning of Signal

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Author Topic:   Aural Alarm: Interpretation of Meaning of Signal
Dave Harnum posted 09-30-2008 09:26 PM ET (US)   Profile for Dave Harnum   Send Email to Dave Harnum  
I have a [a 2003 Mercury 50-HP FOURSTROKE motor], and when the engine has been running for 20 or 30 minutes a continuous warning buzzer comes on and engine starts to slow down. I throttle back to neutral, buzzer goes off and then take off for 5 minutes or more then repeat the cycle. If I shut motor down and let cool down buzzer may not come on at all after an hour of running. Is this [a signal of] an oil [malfunction] or over heat sensor [malfunction]? What do I do next? Plenty of water circulating through the engine and plenty of oil. Thanks, Dave
gss036 posted 09-30-2008 10:15 PM ET (US)     Profile for gss036  Send Email to gss036     
I think you would get better response on the repair forum. I am not familiar w/that particular motor, but, continous beeeeeeeeeeeeeeep is usually overheating and if your engine is going into the safe mode, you may be doing some damage. Oil alarms are beep beep beep and I don't think it would stop if you slow down.
jimh posted 10-01-2008 08:26 AM ET (US)     Profile for jimh  Send Email to jimh     
The sound you hear is an aural alert from the alarm system of your outboard motor. It generally indicates an abnormal operating condition in the motor. If you read the owner's manual for your motor it will explain the meaning of the alarm signals and suggest what steps to take to remedy the abnormal condition.

This discussion area focuses on small boat electrical systems and electronic circuits. For advice on making repairs to outboard motors use the REPAIRS/MODS discussion.

AHI posted 10-02-2008 04:50 AM ET (US)     Profile for AHI  Send Email to AHI     
Most likely the thermostat.....good luck
jimh posted 10-02-2008 05:13 AM ET (US)     Profile for jimh  Send Email to jimh     
Again, this discussion is for electrical and electronic topics. To discuss outboard motor repair, please use the REPAIRS/MODS.

The owner's manual of outboard motors explains how their aural alarm system works, what each alarm indicator means, and what action to take when you hear an alarm. There is a long tradition of publishing owner's manuals with this information in order to convey to the owner of the motor the manner in which it operates. Manufacturers had to do this prior to the invention of the internet. I realize that since the invention of the internet many people now routinely use the internet to gain information about how their outboard motor operates, but the information is still available in the owner's manual.

jimh posted 10-02-2008 05:21 AM ET (US)     Profile for jimh  Send Email to jimh     
If you have a motor in which there is ambiguity about the meaning of the alarm signal, and the alarm signal itself provides no way to deduce which sensor is generating the signal, you can overcome that sort of poor design by applying a simple electrical troubleshooting technique. The next time the alarm signal is given, remove the cowling from the motor, locate the various sensors in the alarm circuit which could possibly be creating the alarm, and then disconnect them one at a time. When you find the alarm sensor that is actually triggering the alarm, the alarm should go silent when you disconnect that sensor.

Prior to making this test, you should investigate the behavior of the alarm system when there is no alarm signal present. Check that disconnecting a sensor does not cause an alarm. If it does, the technique I described above will not work. However, in is fairly common that the alarm system operates as a WIRED-OR logic arrangement, and most of the sensors pull their associated circuit to ground when the alarm condition exists. If that is true, disconnecting them should clear any alarm they are signaling.

jimh posted 10-02-2008 05:29 AM ET (US)     Profile for jimh  Send Email to jimh     
In any alarm system when an alarm occurs there are typically four possibilities:

--(1) the alarm is legitimate; there is a fault condition; it is being properly identified and signaled.

--(2) the alarm is false; there is no fault condition; a sensor has failed and is signaling incorrectly; the rest of the alarm system is operating normally.

--(3) the alarm is false; system itself has failed; all sensors are operating properly but the alarm controller has malfunctioned and is signaling incorrectly.

--(4) the alarm is false; the aural alert device has failed in such a manner that it is signaling an alarm when none exists; the rest of the system is operating normally.

It is generally best to proceed with the assumption of the first circumstance and investigate the operation of the motor to see if it has indeed malfunctioned or is operating abnormally. If no abnormal operation can be established, proceed to test the alarm system for errors.


jimh posted 10-02-2008 05:32 AM ET (US)     Profile for jimh  Send Email to jimh     
Generally to perform any sort of service or repair on a motor you need to be guided by the SERVICE MANUAL. Indeed, attempting to make a repair or investigation without the SERVICE MANUAL is difficult.

Most SERVICE MANUALS will contain electrical wiring diagrams of the alarm system. They also usually contain test procedures to verify the operation of all elements of the alarm system. By following the test procedures in the SERVICE MANUAL an alarm system can be verified to be operating properly.

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