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1991 60 hp Merc. buzzer wont stop!!

T

timmyg

New member
I find myself trying to help out a co-worker. He has a Mercury 60 hp ( s/n od 161933 ) He thinks it is a '91 or '92.

The problem he is having is that the overheat buzzer ( a constant buzzer) goes off while running. It is peeing good and always has and the head is just warm to the touch.


A little history on what he has done...


Last year he had a mechanic look at it and he replaced the oil bottle and replaced the water pump. I told him that there was no way the oil bottle was making the overheat buzzer go off but he had him replace it any way.
No buzzer till about 20 min on the water then OH buzzer and now after it runs about 3 or 4 min the OH buzzer comes back on. So he disconnected it.
About 2 weeks ago I had him run the motor with the muffs on it and when the buzzer goes off unhook the temp sensor and see it the buzzer stops. The buzzer did not stop, telling me that the temp sensor isn't the problem.

Last week he took it to another mechanic and he said that these motors had a problem with the buzzer itself and replaced the buzzer in the shifter control unit. Well he took it out on the lake yesterday and the buzzer is still going off.

Doesn't these things have a control module?
If so, where will I find it?
Is there a way to check the module?

Any other suggestions would be greatly appreciated. This guy has spent about $600 trying to fix this problem and I hate to see him waste any more money on this. The good thing is that there isn't much more left to replace.
 
Re: 60 hp Merc. buzzer wont stop!!

Yes, there is an alarm control module under the hood. It's a kinda sqare (box), but it receives wires from the oil sensor and Merc calls it the "low oil warning module" although it does share it's harness connection with the temp sensor.

You can find it by following a couple of wires from the main harness (engine end).

It is fed by a purple and tan/blue wires - they meet at bullet connectors and continue to the box as purple and tan to the box. It is also fed by two blue wires that come from the oil sensor.

BUT, the temp sensor is really it's own circuit (just shares the tan/blue line from the connector at the oil alarm up to the buzzer).

The temp sensor is a simple resistance circuit. When it gets (hot), resistance goes down allowing the power in the line into it to go to ground - completing the circuit and the buzzer goes off (no control module required).

Since disconnecting it has no effect I would be looking for a short somewhere in the tan/blue wire between the bullet connector for the temp sensor and the plug of the engine harness.

It sounds like somewhere in that stretch, it's going to ground and causing the buzzer to do it's job....
 
Re: 60 hp Merc. buzzer wont stop!!

There should be a module in '91. The oil bottle sensor is a common problem. The blue wires from the bottle go into the module on the stbd. side of the motor. The only other way this happens is when the tan/blue buzzer wire it touching a ground somewhere. Usually inside the control unit. That wire is easy to pinch in the case.
 
Re: 60 hp Merc. buzzer wont stop!!

galamb said:
Yes, there is an alarm control module under the hood. It's a kinda sqare (box), but it receives wires from the oil sensor and Merc calls it the "low oil warning module" although it does share it's harness connection with the temp sensor.

You can find it by following a couple of wires from the main harness (engine end).

It is fed by a purple and tan/blue wires - they meet at bullet connectors and continue to the box as purple and tan to the box. It is also fed by two blue wires that come from the oil sensor.

BUT, the temp sensor is really it's own circuit (just shares the tan/blue line from the connector at the oil alarm up to the buzzer).

The temp sensor is a simple resistance circuit. When it gets (hot), resistance goes down allowing the power in the line into it to go to ground - completing the circuit and the buzzer goes off (no control module required).

Since disconnecting it has no effect I would be looking for a short somewhere in the tan/blue wire between the bullet connector for the temp sensor and the plug of the engine harness.

It sounds like somewhere in that stretch, it's going to ground and causing the buzzer to do it's job....
Click to expand...


Thanks galamb,
If I'm understanding you correctly, you are saying that the "low oil warning module" wouldn't be the problem with the temp buzzer?

I haven't looked at it yet but plan on going over to look at it Mon. or Tues. evening.
I thought about a short but he said that when he turns on the key the buzzer will "test sound" as it should then after running it will come back on. Thats why I thought it may have been a bad sensor turning the buzzer prematurely.

I will give it a good look and report back my findings.
Thanks again for your help.


Timmy
 
Re: 60 hp Merc. buzzer wont stop!!

Sounds like a short, but it could have a water blockage near the sensor causing the buzzer to go off. The short is probably right near the buzzer itself.
 
Re: 60 hp Merc. buzzer wont stop!!

Correct, I don't believe the module is the issue at all, but the harness wires that ultimately connect to the temp sensor are very close to that module - in fact they (tee off) and connect to both the temp sensor and the oil module.
 
Re: 60 hp Merc. buzzer wont stop!!

galamb said:
Correct, I don't believe the module is the issue at all, but the harness wires that ultimately connect to the temp sensor are very close to that module - in fact they (tee off) and connect to both the temp sensor and the oil module.
Click to expand...

Thank you again.
I will look at it and see what I can fiind.

Timmy
 
Re: 60 hp Merc. buzzer wont stop!!

Thanks again galamb, your info was very helpful.

I went by and looked at it today. I checked all the wires on the motor and found no shorts. I used a jumper wire to test the temp sensor wiring and everything checked out fine. So it seems that the temp side is working as it should. We tried to test the temp sensor by putting it in hot water but I don't think it was hot enough.

We found and removed the module.

There are two blue wires (from oil bottle) one purple wire (power to module I think ) one black wire ( ground) and one tan and blue wire ( to buzzer)

From what I understand the module is a separately powered relay that when it receives a ground from the oil bottle breaks it into a pulsing signal much like a turn signal relay on a car.

Is this correct?

What we found is that it looks like the module is bad after all and sticking in the on constant position giving off a constant buzzer like the overheat buzzer.

Is it possible that the two blue wires could have been connected backwards? Where does the oil bottle gets it's ground? or is it a floating ground through the two blue wires and gets it's ground from the module?


With the module removed the overheat buzzer should and seems to work properly he just has no low oil warning.


Timmy
 
Re: 60 hp Merc. buzzer wont stop!!

The purple wire is the power feed from the keyswitch - so the unit is only powered when the key is in the "on" position.

The two blue wires are a to/from circuit (no ground). The oil sensor is basically a switch - off when there is oil, on when it gets low. When it detects low oil it completes the circuit feeding power through one of the blue lines back to the control module (which as you note, is grounded through the black wire).

The tan/blue wire, which is also fed by the temp sensor, goes to the harness and up to the buzzer. (the temp sensor is just a resistance circuit - when it's "hot", resistance goes down to near zero completing the circuit sending continuous power (beeeeeeeeeeeeep) up to the buzzer.

And yes, if the oil control module gets a completed circuit from the oil sensor it will send intermittent power (beep beep beep) up to the buzzer.

It makes no difference if the blue wires are reversed since it's entirely a positive circuit.

If the module is shot and giving you the constant beep, you could leave it disconnected (just remove the tan/blue wire from the bullet connector that connects to the tan (should be just a tan wire) on the module) and the temp sensor will function as normal.

A quick test can be done with a volt meter to see if the module is your problem. With the key on position and the tan to tan/blue disconected, set the volt meter for at least 12 volts - positive (red) lead to the tan and negative (black) to any good grounding point on the engine.

If the circuit is energized then you know the module is toast...
 
Re: 60 hp Merc. buzzer wont stop!!

Thanks again galamb,

Is this module something he would need to get from Mercury or would he be ok getting one online. At this time he is planning on getting a repair manual, a module and maybe a new temp probe for good measure.

Do these motors have a built in safety mode (limp mode if you will ) like my Yamaha has?

Timmy
 
Re: 60 hp Merc. buzzer wont stop!!

You might find a replacement from CDI/Rapier (don't know).

The Merc part lists for about $115.

If it is shot I might be personally inclined to just leave it disconnected.

A "full" oil tank (under the hood) gives you about 7 hours of runtime worth of oil - far more than most of run in a single outing.

I would weigh checking the oil before each outing against the 115 bucks for a new module - that doesn't tell you if the oiler is working, instead, "only" if there is oil in the tank....
 
Re: 60 hp Merc. buzzer wont stop!!

Sorry, missed the second part of your question.

No, there is no "guardian" on this model.

There is a rpm limiter but it is only fed by the trigger and will ground out the ignition if the motor exceeds "x" rpms, but the (horn) warning system does not feed that module at all....
 
Re: 60 hp Merc. buzzer wont stop!!

It kinda sucks that Mercury will go to all this trouble to let you know when your oil level is low but have no way to warn if the oil getting to the motor.:confused:

It also sucks that he has spent sooooo much time and money trying to fix this problem when I just spend about 1/2 hour looking at it and of course with all of your help and even though it isn't "fixed" we know what the problem is and that the temp warning system is working properly.

I guess this is an example of the difference between a mechanic and a parts changer.:rolleyes:

Do you know at what temp the warning buzzer should come on?
And based on the S/N OD 161933 , can you tell what year it is?

And once again, THANK YOU SO VERY MUCH for all your help on this matter.

Timmy
 
Re: 60 hp Merc. buzzer wont stop!!

Yes, the "oil sensor" made no sense to me for quite a number of years for exactly the reason you state.

Merc did however, in later years, add a "motion detector" at the oil pump which will alarm you if it stops working (far more important in my opinion than whether you have oil in the tank which could be easily checked visually).

Anyhow, the temp sensor "goes to ground" at about 195 degrees and will continue to alarm until the temp gets back below 178 (I think - might be 175 or so) - so it has to be quite a bit "hotter" than the 143 operating temp of the motor.

The sensors are pretty simple in design, fail fairly often, but fortunately, when they "bust" you will get a false alarm - they don't quietly die and allow you to toast your motor while they sit there doing nothing.

And that production number (serial) makes it a 1992 model.
 
Re: 60 hp Merc. buzzer wont stop!!

I know i keep saying this but I can't say it enough.

From me and my friend, THANK YOU SO MUCH for all your help!!!!!!!!

Timmy
 
Re: 60 hp Merc. buzzer wont stop!!

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Not sure if you all are on this forum anymore, but wanted to register and comment thanks for the info. This link was a top result for the problem I was looking for. I have the same problem happening, but I'm in the early stage. Constant buzz, ran the motor and pulled the temp sensor today, still ringing. Plan to go down the path of more testing with ya'lls info above. Mine is a 1995 Mercury 60 HP Pro Series Model # 1060412RT Serial # 0G14525. I'll pull the two oil tank blue wires tomorrow just to see if something happens, but if nothing changes I'm thinking short on the temp blue/brown wire or module.

Cody
 
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