At what water temp does alarm horn go off?

[calm like a bomb]

Does anyone know what factory setting the water temperature alarm horn is set to go off at on a 1997 Mercury XR-6 150 hp?It is the carbed model.<br /> I installed a good Teleflex water temperature gauge this afternoon and it works fine but the alarm horn still does not seem to operate correctly(fails to give a test beep when the key is first turned to the "On" position).<br /> Until I can get the alarm horn working I will have to rely on the new water temperature gauge to make sure it is cooling correctly and would really like to know the safe limit on the water temperature range.Thanks!

 

[WillyBWright]

Re: At what water temp does alarm horn go off?

The test beep has nothing to do with the overheat sensor. It's either a warning module problem or the alarm itself has failed. The alarm is a sort of idiot light. Gauges are ALWAYS better, but you have to watch them. The alarm is nice to alert you to a problem, but the motor may already be damaged when it finally sounds.

 

[gss036]

Re: At what water temp does alarm horn go off?

The overheat alarm will go off at about 240 degrees and if you allow it to cool down, it will rest about 230 and go off again when you reach 240. The temp gauge sender is usuall on the port head and the overheat on the starboard side.

 

[calm like a bomb]

Re: At what water temp does alarm horn go off?

Great information gentlemen and I appreciate it.<br />I watch my gauges like a hawk but wanted to know what temp would trigger it. (240* is hot!!)<br /><br /> I ran her this afternoon and the temp were good according to the new gauge I installed yesterday.<br /> She ran right at 140*..that sound OK? The surface water temp in Charleston was about 56* today.<br /><br /> I will have to troubleshoot the alarm buzzer though to get it working correctly (temporary alarm signal when the key is first turned to the "On" position).One long/two short.I will rely on the temp gauge for sure but still would like to troubleshoot the buzzer. <br /> <br /> The buzzer is hooked up to the purple wire from the ignition and the tan wire/blue stripe from the alarm sending unit.<br /><br /> The water temp is connected to the plain tan wire from the sending unit and is properly wired to 12V positive and a good ground with the backlight wired into my other gauges.<br /><br /> I'm wondering if the sender to the warning buzzer is faulty because the horn does not function even though it is wired correctly.<br /> Is there any way to test the sending unit to the buzzer or a test on the buzzer itself?<br /> Thanks again for the help!!

 

[DHPMARINE]

Re: At what water temp does alarm horn go off?

Wow,I guess I'm getting outdated here.I would have thought 240 degrees was melt down.What happened to my 163 degree wax crayon.<br /><br />DHP

 

[gss036]

Re: At what water temp does alarm horn go off?

The 240 degree F +/- 8 degrees is straight from my Merc manual for my 1989 200 hp Merc. I have only had mine go off twice, once in a kelp bed and the other when the impeller spun.

 

[DHPMARINE]

Re: At what water temp does alarm horn go off?

gss036,<br /><br />I just looked at the manual and you are correct.I didn't think the alarm would wait that long to warn you.<br /><br />I also notice the thermostat is a 143 degree,so I'd expect tempts no higher than 150,and would be nervous at 160 or so.<br /><br />DHP

 

[Laddies]

Re: At what water temp does alarm horn go off?

Thats why we call that a self destruct horn, it's like the OMC red light of the 60s that came on just after the engine setup

 

[calm like a bomb]

Re: At what water temp does alarm horn go off?

From what I an hearing from you gentlemen it does not sound like I need to devote too much time or energy to replacing the "self destruct horn" since by the time it finally goes off you likely have much bigger problems anyway.<br /><br /> Keeping a close eye on the water pressure gauge and the water temperature gauge should be a much safer way to monitor the condition of the cooling system than having to rely on the alarm horm to finally go off after the engine has reached meltdown temperature anyway?

 

[gss036]

Re: At what water temp does alarm horn go off?

I cannot agree with that theory Calm, The two times that mine went off, I stopped the engine, cleared the kelp on the first signal. Second time, let it cool down, then went 8 miles at mid- throttle to get back home and then put in a new water pump. That was about 5-6 years ago, have done just the impeller since then and still running strong. At the price on new engines, hopefully I will get a few more years out ot it. If not, I will repower w/a 250hp E-Tec.

 

[KCLOST]

Re: At what water temp does alarm horn go off?

You guys have to look at what the Overheat sensor is measuring... Is it measuring Metal temps on the head or water temps that circulate though the jacket somewhere.<br /><br />If it measure metal temps on the head (and in no way touches water) that 240F level is the correct overheat alarm reading. Metal even aluminum will not melt at that point so it is important and useful. But if it is measuring water, that is another story, and you need to find out what that overheat temp is rated for... <br /><br />And even though the t-stats are rated for 143F, that does not mean that the water will not go above that level even if everything is working properly. That is only the temperature that the t-stats will open.<br /><br />My bet is, that your overheat sensor is measuring metal on that year of engine.. And I'll also bet that your temp sensor (for the guage) is measuring water, otherwise you would have higher readings than what you posted. And since your Alarm is not working/testing itself, after the turn of the key, I bet you have the oil injection system disabled and are running premix?????<br /><br />Let us know..

 

[gss036]

Re: At what water temp does alarm horn go off?

KCLOST, acutally, they both measure metal tempature. One on each head. The overheat on the starboard and temp sensor on the port. There are recessed holes in head for them to fit into.

 

[calm like a bomb]

Re: At what water temp does alarm horn go off?

KCLOST,<br /><br /> It does have the oil pump disabled and I do run premix now.How does this factor in?

 

[andy6374]

Re: At what water temp does alarm horn go off?

What KCLOST is refering to is that the "beep beep beep" sound you hear when you turn the key to the "ON" position is sent from the warning module (actually called a lubalert in the manual). If you have the oil injection disabled the warning module is removed as well, and hence you don't get the "beep beep beep" self-test.<br /><br />-andy

 

[KCLOST]

Re: At what water temp does alarm horn go off?

Andy is correct. <br /><br />All you need to do to test the overheat sensor is follow the overheat sensor wire to the terminal block.. Ground that terminal to the block itself with the ignition key turned on (don't need to have the engine running)... If it works, the alarm will sound....<br /><br />gss, I know the design, but I'm not sure about a 1997 engine. If you are sure that's good.<br />I just think his temp readings are low to be measuring metal on the head, but again we are talking about a 1997 engine, not a black max from the late 80's..

 

[calm like a bomb]

Re: At what water temp does alarm horn go off?

Great info guys....since it is now pre-mix the alarm is no longer a factor.I'll just pay close attention to the pressure and temp gauges for peace of mind.Thanks very much!!

 

[andy6374]

Re: At what water temp does alarm horn go off?

You are still a little confused. You can still have the warning alarm (i.e. the buzzer) but it just won't do the self-test beep when you turn the key to the "ON" position. However, it is much better to pay attention to the water pressure gauge then to wait for the alarm to go off.

 

[calm like a bomb]

Re: At what water temp does alarm horn go off?

10-4 on the alarm..and I'll watch the gauges like a hawk too until I get used to this engine and it's characteristics.Thanks to all..

 

[Mandella69]

Re: At what water temp does alarm horn go off?

Just curious. I have a 1986 150 Black Max. What type of oil injection system does it have?

 

[Texasmark]

Re: At what water temp does alarm horn go off?

For what it's worth.<br /><br />Just acquired an '02 3 cyl 90 hp. In short I had an overheat problem and a stuck closed thermostat was my problem. My therm was marked 120F and my service manual says the alarm goes off at 190. My alarm worked worked just fine but I too do not have the squeak of the horn when first energizing the ignition...as the manual says I should. I did the "ground at the power head" test for the over temp sense wire and it worked too. The first time it went off, I felt the top of the water jacket and it was hot; not real hot, but hot enough to tell you that the horn went off correctly.<br /><br />HTH<br /><br />Mark