Overheat Alarm

[Buddy Gold]

The previous owner mounted a new overheat alarm because he said the old one was not loud enough to be heard in the cockpit. He never got around to connecting it so it is just sitting there with the 2 wires attached to nothing.  I would like to hook it up but there is no markings on the alarm that are visible for me to try and look up where those wires should be attached.   Any suggestions on where those two wires should go.

[KWKloeber]

Depends on your engine.
See previous post suggesting you post your boat/engine info in a signature.
Need a pic of the thermostat cap.

[scgunner]

I didn't even know these things had overheat alarms. My motor has overheated more than once and the only alarm I remember hearing was the "Oh ####!" from my own lips when I saw the temperature gauge pegged.

[KWKloeber]

Kevin

Your engine?  M25?

[Noah]

Kevin—Overheat alarm conversion:
https://www.catalinadirect.com/shop-by-boat/catalina-38/electrical/high-temp-alarm-retrofit-m-18-m-25-m-25xp-m-35/?SearchResults=1

[Ron Hill]

Buddy : It's impossible to answer your question as the picture about your M35 engine alarm leaves MANY questions !?! 
Your picture doesn't explain how the shown alarm operates?  It looks like it has a red light visual alarm, audio? and if? there is a temperature setting inside that case???

If there is a temperature setting inside for 200F???  Then I'd guess that the red wire would go to the same threaded pole on the temp sender (on the engine thermostat) and the black wire to ground???  This is all speculation!!!! 

Need much more information!!!


A few thoughts

[Buddy Gold]

I took the cover off the alarm and there is a Tiny circuit board inside but no other markings as to MFG or anything else for that matter.  It's a Universal 35..

[scgunner]

Ken,

Yes, it's an M25.

[Ron Hill]

Ken and Kevin : Buddy is correct the engine in the picture is a 4 cylinder M35 !!

A thought

[KWKloeber]

@Kevin

What one has, is a function of both the engine and the panel. 

First -- setting the stage -- unlike the temp alarm, the oil alarm is easy and is driven by a simple OFF/ON, NO-GO/GO pressure switch.  It completes a circuit that sounds the alarm.  On older engines, the key switch powers the alarm and the switch simply completes the ground to sound the alarm.  On the "A" and "B" engines it's a complicated hot mess. But w/o getting into he weeds the same applies -- the ON/OFF switch controls the alarm.

The temp alarm is not so easy.  A gauge sender is not ON/OFF.   
I don't know what year a "switch" }uggggh{ was made on the 34, but early 30 and 34 panels had a circuit board that "reads" the impedance of the temp gauge sender (from the wire from the sender to the temp gauge.)  At whatever present ohm impedance, the circuit board tripped the temp alarm.  That board WILL fail and there's NO replacement.  The supplier across the pond where Seaward got them no longer makes them.

Introduce the XP, and the "temp switch" (also continued onto the "A" and "B" engines.)  You can see the temp switch in Buddys picture (the yellow, Sta-Kon, non-marine-grade terminal,) and in the CD picture.  Thats just a plain old ON/OFF switch.  The alarm is powered by the key and the switch completes the ground.  Naturally for the gauge and switch to work properly, the Tstat cap needs a good ground, which is sometimes an issue.
https://c34.org/bbs/index.php/topic,10733.msg83637.html#msg83637

You don't need a new TStat cap for 160 beans - you drill/tap the old TStat cap to add the new (1/8" npt) temp switch.  Ones who did the ammeter/voltmeter mod have a spare harness wire to use for the temp switch. 
Or run a new wire. 
Or wire the temp gauge to the oil switch -- either one will sound the alarm and the temp gauge reveals which is the problem.

The CD temp switch is GOOD the Westerbele switch is BAD (funky terminal that requires an oddball (called a Packard 56) wire terminal.)

[KWKloeber]

@Buddy

You have an M-35BC engine.  An important distinction when discussing parts and systems on it.
"C" means it has the "Catalina wiring standard."

A temp alarm gets wired to the temp switch (on your TStat cap, has the yellow wire terminal.)

That's a 12v, exterior, home security system strobe/100dB siren.

Its red wire gets powered by the key switch (or other 12v source) and the black wire goes to the temp switch. 
Yours switch appears to have a green wire that goes to the OEM alarm.

You can power the alarm (red wire) from the fuel pump power or the alternator field excite wire (or terminal.)  Both receive power from the key switch.

This is also a very nice, adjustable alarm that I have used a few times.



and the combined C-H light/alarm

[Buddy Gold]

What I am now thinking is this alarm was meant to just piggy back off of the OEM alarm and has no Social Redeeming value of it's own.

[KWKloeber]

Buddy

I would agree that s/he was likely going to have both alarms. Alternatively just put a louder piezo alarm replaying the one at the panel.

Note my comment about the engine, suggest you update to signature to 35BC, a COMPLETELY different engine than the 35.

[Buddy Gold]

I hooked up the alarm piggy backed to the OEM alarm. I now understand what the intended purpose was and why the idea was abandoned.  It was meant to provide alarm to the cabin because the alarm from the helm might not be heard if you were down below running on auto pilot.   The alarm was loud enough for people in a 10 block radius to run for cover.  If I am ever underway single handed with the motor running asleep in the cabin I will hook it up. But I don't ever see those circumstances ever happening.

[scgunner]

You really think being down below while motoring with the autopilot is a good idea?