Constant warning horn

[Cruise149]

I have a 1993 mercury 2stroke 115hp outboard. Horn gos off constant sound speraticly has sat for 2 days turned key on test sounded then constant horn went off turned key off and on a couple times it quite took it out for a test ride was fine for 20min then started very lightly and once in a while then full blown constant sound, seemed like when I played with the throttle it would stop and start but couldn't get it to do it all the time. Any suggestions? Maybe a wire in throttle area ? But even when sitting I had left key on and walked away to grab a screwdriver all of a sudden it chirped again and then full horn with nothing moving(was on trailer at this time)

 

[Texasmark]

The horn is wired from the ignition switch red/purple stripe or purple wire for 12v. On the ground side, it gets ground (batt -) from either the OT sensor, tan wire on the rear of the engine block near the plugs, or the low oil sensor which sends the signal to the modulator module and rather than the 111111 for OT, it is 101010101 to identify oil.

If you have a horn blowing with the key off and the engine not running you have it wired directly to the battery, or the ignition switch is shorting internally red to red/purple and a short in the wiring harness down circuit of the horn or a shorted OT sensor back by the plugs.

 

[Cruise149]

Thanks, no the key was on not off when this was happening, I am going to pull controller apart and check for a shorting wire have already checked on the engine block end

 

[Texasmark]

Disconnect the tan (should be tan or tan with light blue stripe) somewhere....If in the remote to engine 6-8 pin elect. plug, just disconnect that, or sometimes it and another wire (PTT) are run along the outside of the remote cable and are not part of the main connector, but separate bayonet connections available where it is for connection to the engine.

With the switch off, measure the voltage at that pin...looking back toward the control, not toward the engine. It should be zero. Switch the key to ON and it should read your battery voltage....12+ volts. Turn the key off and measure the resistance to battery -, ground......should be something higher than an ohm or two. If a low resistance number, then you have a short in your wiring between your horn, which may be located IN the control, or adjacent to it zip tied to the outside of the wiring harness in the general area of the control. If all that works, your control is working, you don't need to tear anything apart.

If you haven't found a smoking gun as yet, follow your tan or tan/lt. blu stripe wire to a module (if your engine is equipped with a modulator for low oil....1010101 rather than 11111 which is OTemp) in the engine and pull the plug. If the noise stops, replace the modulating module.

 

[gm280]

:welcome: Cruise149 to the iboat community. Always great to have a new member...

Texasmark offered some great advice and knowledge there. Only thing I would say is if this was working correct and just started doing this, it is time to check all the connections on everything because is sounds like you could have some corrosion going on with some connections. JMHO

 

[Cruise149]

Thanks I will try that, couldn't tell you if it's a new problem or a speratic issue as this boat is new to me as of a few weeks ago, first issue I had alarm for oil as the magnetic let go of float took car of that issue and next time out this started. I will post my results. Thanks guys.