Alarm horn??

[Aquamaniac]

Was trying to sort out the wiring on my 1990 200 Striper......
Can't seem to locate any alarm horn. Removed instrument panel, nothing in either console compartment, nothing anywhere I can see inside entire console.
PO ('fine fella'..you recall he made no mention of removing jack plate) said alarm had gone off and he supposedly replaced thermostats, impeller, etc..
Well.....beginning to wonder if he just removed the alarm! Engine not getting hot (we replaced thermostats, pop off valve, and checked impeller.). Sure would like to know alarm would work though if need be.
So where is is normally located?
BTW I did get a hold of shop manual for Merc 150 and it shows wiring diagrams.
Appreciate any help.
Thanks.

[Georgie]

Plenty of ways to hotwire the horn and put it in odd locations, but in my experience it's typically wired to, and located in the general proximity of, the ignition switch.

Farley, is the alarm circuit for Merc's tan like OMC?  

Better yet, AM, just see what color the wires are near your temperature switches in the engine, and look for that color wire inside the console.  If your wiring hasn't been completely jury-rigged or cobbled together with mis-colored scraps over the years you should be able to track it down.

[seabob4]

Ryan, I was thinking it was either solid tan or tan w/blue stripe.  I was right...http://www.maxrules.com/fixmercwiringcodes.html

[fitz73222]

It depends on which wire harness you have but should be tan (coming from the temp switches in the heads) and keyswitch activated 12V (purple) going to the hot horn, near the keyswitch. Old style hot horn is about 1 3/4 diameter X 1" thick. bulky plastic and metal wrapped in a plastic mesh or new style Piezo style horn about the size of a quarter X 1/2" thick, black plastic near the keyswitch. Find the tan wire coming from the engine harness and coming from the keyswitch and see where they terminate or are they cut and wrapped. It doesn't have a temp gage by any chance instead? The correct horn kit is 816492A9. Is your engine oil injected or pre-mix? The other way to find if you have a hot horn or not is to probe one of the tan wires with a test light tip, nail anything that will pierce the wire and touch the head; coming from either cylinder head, turn the keyswitch on and ground it to the cylinder head and the horn should sound.Sometimes people remove the hot horn because the warning module is bad back on the engine and horn won't shut off when you turn the keyswitch on. Since you have a FrankenMerc, I have no idea what you have there so I can only tell you what should be there.

[Aquamaniac]

Do have temp gauge. Pulled switch plate as well. Spotted a black plastic horn that is all glommed into the wiring harness going to ignition. I see a tan/blue stripe wire that has been cut. Mean anything ?

[seabob4]

Do have temp gauge. Pulled switch plate as well. Spotted a black plastic horn that is all glommed into the wiring harness going to ignition. I see a tan/blue stripe wire that has been cut. Mean anything ?

Click on my link above, check what the tan w/blue stripe is for...

[fitz73222]

Do have temp gauge. Pulled switch plate as well. Spotted a black plastic horn that is all glommed into the wiring harness going to ignition. I see a tan/blue stripe wire that has been cut. Mean anything ?

Click on my link above, check what the tan w/blue stripe is for...

What do you know about wiring anyway Bob?

[seabob4]

Do have temp gauge. Pulled switch plate as well. Spotted a black plastic horn that is all glommed into the wiring harness going to ignition. I see a tan/blue stripe wire that has been cut. Mean anything ?

Click on my link above, check what the tan w/blue stripe is for...

What do you know about wiring anyway Bob?

Not a damn thing Farley.  Stayed at a Holiday Inn Express once...hated it...

[Aquamaniac]

Hey Bob,
Hmmmm....alternate temp switch to horn.....
Bad news is that when I fired up the beast on the muffs, the temp gauge did not seem to budge.
Guess I need to sort out sender vs gauge. Not to mention if alarm horn will still work.

[seabob4]

Hey Bob,
Hmmmm....alternate temp switch to horn.....
Bad news is that when I fired up the beast on the muffs, the temp gauge did not seem to budge.
Guess I need to sort out sender vs gauge. Not to mention if alarm horn will still work.

Easiest way is to ring it out.  Check for continuity between the wire coming off the temp sender on the motor, and bot the tan and the tan w/blue stripe under the helm.  Hopefully, you'll get continuity on one or the other...

[Aquamaniac]

Hehehe.....I know for a fact Bob knows more about wiring these than I EVER will!
What is throwing me off is I don't see the tan /blue wire connected to the temp gauge.
Have been trying to sort out the wiring diagrams I can find in the service manual.....but not having much success finding a diagram of the gauges other than tach,trim indicator, and alarm horn.
Will try to post a couple pics of gauge wiring.

[Aquamaniac]

Gauges are tach, battery, temp, tilt, fuel left to right. Don't see any tan/blue on the temp gauge. Will try to find it on motor.
The two loose white wires I removed.
Have to confess.....I love wiring almost as much as plumbing under the house  :P

[seabob4]

Tom,
IIRC, both tan wires were butted together in the engine harness...both the same circuit.  Allowed a lead to run to the temp gauge, and a lead to the warning horn...IIRC.

Anyway, attach a long length (long enough to reach from the motor to the helm) to the wire off the temp sender on the motor.  Then, with your multimeter set on continuity (the little "speaker" looking symbol), touch one probe to the wire on the gauge, the other to the long wire you attached to the wire at the temp sender.  If you get an audible tone (or the multimeter display reads 000), then you know you have continuity.  Do the same for both the tan and the tan w/blue stripe...

[Georgie]

Bob,

I'll certainly trust you on this because I struggle with electrical stuff at times, but wouldn't the temp gauge and overheat alarm need to be on a separate circuit using a different wire?    I can't imagine the the basic on/off switches in the cylinder heads would function the same as a rheostat-type temp switch which would need to be able to give variable feedback to the gauge, right?...hence the need for both an all-tan and a tan-blue circuit?  I've honestly never run a temp gauge so I have no firsthand experience on this one.  What you got???   Do the Merc switches work differently than the OMC switches?

[seabob4]

Ryan,
The senders are resistance based, just like a fuel sender.  Variable resistances give different gauge readings.  Resistance too high (or too low)?  The circuit is closed and the horn sounds.  My "guess" is that, being resistance to ground, once the resistance gets to a certain point (over temp), it shorts to positive and sounds the alarm.  Much the way a kill switch works by shorting to the ign positive and grounding the coils...