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Author Topic:   1998 Optimax 150 Warning Horn
Kanawha1 posted 06-20-2009 02:12 PM ET (US)   Profile for Kanawha1   Send Email to Kanawha1  
Proud new owner (to us) of a 1998 Dauntless 180 with a 150 Optimax. Motor runs fantastic but have a horn [malfunction]. When I turn the key to the RUN position the horn only occasionally beeps. I thought [the inconsistent beeping of the horn] was [being caused by] low voltage, so I replaced the starting battery with the battery prescribed in the manual. Still [the warning horn] won't beep [every] time, and when it doesn't the CHECK ENGINE light stays illuminated. No [problems] with the engine running, and my fish finder and analog gauge both read about 14-volts. I have checked both the starting and trolling motor batteries, and they are fine. Just need a new warning horn?
jimh posted 06-21-2009 08:04 AM ET (US)     Profile for jimh  Send Email to jimh     
On Mercury motors that I have seen, when the ignition key is turned to RUN from OFF, and before the motor is cranked over, the warning horn sounds briefly to signify that it works. The horns usually sound one of the following two cadences:

BEEEEEEEEP Beep Beep (Morse code "D")


BEEEEEEEEP Beep Beep Beep (Morse code "B")

I don't know if this sequencing of the beeps is built into the sounder itself, or if it comes from the unit controlling the sounder.

I don't have the service literature for the 1998 OptiMax, but on some later versions of the motor the service literature mentions that the warning horn sounds only a "single beep" on initial power on.

Kanawha1 posted 06-21-2009 10:13 AM ET (US)     Profile for Kanawha1  Send Email to Kanawha1     
Thanks, I occasionaly get the single BEEEEP, all four warning lights flash then everything normal. The manual indicates it's either a low voltage issue or a sensor not working properly. I'm 99% certain it's not a voltage issue because I'm well above the threshold of 10.4V I am presuming the horn is the culprit because if other sensors aren't working the engine is supposed to go into some type of "SAFE" mode (reduced RPM's)?
jimh posted 06-21-2009 01:17 PM ET (US)     Profile for jimh  Send Email to jimh     
The sounder likely operates on the 12-Vdc power of the battery. Connect a voltmeter across the sounder terminals. Operate the ignition switch to the RUN position from the OFF position. Observe the voltmeter indicator for a brief upswing indicating voltage was applied to the sounder. Compare the aural output from the sounder with the applied voltage. If there is no correlation the sounder is probably not operating properly.
jimh posted 06-21-2009 03:19 PM ET (US)     Profile for jimh  Send Email to jimh     
As an alternative to a voltmeter, whose transient response might be hard to appreciate, wire a small indicator LED in parallel with the horn. The LED should illuminate when the horn is being supplied with 12-Volts. This would give you a visual indicator that the horn ought to be making an alert sound.
18 Ventura posted 06-22-2009 10:35 AM ET (US)     Profile for 18 Ventura    
Run a search for TPS (Throttle Position Sensor) error. The TPS is very finicky on this vintage OptiMax. If the check engine light is on and the horn is sounding, the TPS is a likely suspect. (I have this issue with my 1998 135 OptiMax from time to time.) If you bump the throttle at all while the engine isn’t running (or in gear, it seems) you can trigger the TPS error. Next time you get this error, shift out of gear and into neutral firmly, making sure the throttle handle is “centered” as best you can. Shut of the engine, and restart after a few seconds. If the TPS was triggering the alarm, both the check engine light and horn should not come back on. If this doesn’t solve the problem, it may at least help with your troubleshooting efforts.

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