Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating?

[Ant-Knee]

Hello all,

Well my 98 merc 150 Model 1150422UD, Serial 0G740674, has been running awesome, And is actually still running awesome, ..

My last trip out the overheat alarm starting going off, but boat was not over heating..
I have the alarm and I also have another temp gauge, The gauge reads 160 at idle in my driveway/ and in the water but alarm is sounding.. Boat could be ice cold and alarm is still sounding...

I am unsure where to start, I have one sensor in one head that goes to my gauge and in the other head what I think is the temp sensor , I disconnected it to see if that would stop the alarm but it did not, Tells me the problem is not that sensor.. What else can I check to see what the problem is???

Thanks Guys,

Ant...

 

[CharlieB]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

Some models used the same alarm for oil and overheat.

Is the alarm on constant when the key is on? Is it a solid tone or a very rapidly beeping tone?

Unplug BOTH temp sensors, if the alarm remains on chances are you are having an oil alert.

The oil alert is supposed to compare a rotation sensor on the oil pump to an ignition pulse from one of the coils, if there is a difference in the two signal OR if the oil level sensor in the onboard tank cap, then alarm sounds.

Crack the onboard oil tank cap loose while at an idle, let the oil fill to overflowing then retighten the cap. Many times this will cure it. If not then spark test that cyl that the coil has an extra green wire leading to the alarm module. If no spark then troubleshoot the ignition problem.

Do you have a factory service manual, as the aftermarkets leave out far too much detail when troubleshooting problems like this.

 

[Ant-Knee]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

Some models used the same alarm for oil and overheat.

Is the alarm on constant when the key is on? Is it a solid tone or a very rapidly beeping tone?

Unplug BOTH temp sensors, if the alarm remains on chances are you are having an oil alert.

The oil alert is supposed to compare a rotation sensor on the oil pump to an ignition pulse from one of the coils, if there is a difference in the two signal OR if the oil level sensor in the onboard tank cap, then alarm sounds.

Crack the onboard oil tank cap loose while at an idle, let the oil fill to overflowing then retighten the cap. Many times this will cure it. If not then spark test that cyl that the coil has an extra green wire leading to the alarm module. If no spark then troubleshoot the ignition problem.

Do you have a factory service manual, as the aftermarkets leave out far too much detail when troubleshooting problems like this.

It is a very rapidly beeping tone, If I turn the key to the on position, The alarm beeps couple times then stops ( this is normal) Once motor is started then the beeping starts motor can be ice cold and still beeps... I removed the oil containers as I mix the oil right in my tank with the gas...

Ant...

 

[hl]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

The heat sensor should be a continuous beep. If it going off without the engine being hot have the sensor checked. They can be bad and signal overheating for no reason.

 

[Ant-Knee]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

Where is the sensor located on motor? How do I check it?

Thanks,

Ant...

 

[hl]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

It has been a while since I messed with sensor, It is located on right head (looking from behind the engine) I am thinking it is round with a cover held in by two screws. There will two wires leading to the sensor. Can not remember for sure but thinking one wire is blue and the other is brown .

 

[carholme]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

Your s/n comes up as:

MERCURY - (150 H.P. (1998 ))
Serial No: 0G740674 Model No: 1150422UD

Parts and Service Bulletin list for s/n 0G740674:

Search Results - Crowley Marine

The service manual you require is P/N: 90-82405

From 3E-8 of the manual:

The oil injection warning sound is an intermittent
“beep”, “beep”, “beep”, etc. The overheat warning
sound is a continuous “beep” (not intermittent).

If you do not have the manual, see my message to you in Notifications at the top of the page.

Gerry

 

[Dukedog]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

It is a very rapidly beeping tone, If I turn the key to the on position, The alarm beeps couple times then stops ( this is normal) Once motor is started then the beeping starts motor can be ice cold and still beeps... I removed the oil containers as I mix the oil right in my tank with the gas...

Ant...

Did you remove everything relating to tha oiler "including tha module"?..........Sounds like this is gonna be tha problem.

 

[Ant-Knee]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

Did you remove everything relating to tha oiler "including tha module"?..........Sounds like this is gonna be tha problem.

No I did not remove the Module, I was not sure if it was needed for anything else...
Is it ok to completly remove the module??

Only thing I removed was the oil tank on the engine and the big gallon tanks that would sit on my deck..

Thanks for your help.. Sorry bout the mix up guys, I Thought the steady beep tone was for the oil and the intermedit beeping was water temp, Guess I wass backwards with my beeps...HeHe!!!

Ant...

 

[Dukedog]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

Yeah. Need ta remove everything related to tha oil injection. There are lotsa threads about it that also give ya part numbers for tha "kit" ya gonna need. I would get into it a little more but have a terrible hangover this morning! Goin' away beach party last night.........:faint:

 

[Ant-Knee]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

Yeah. Need ta remove everything related to tha oil injection. There are lotsa threads about it that also give ya part numbers for tha "kit" ya gonna need. I would get into it a little more but have a terrible hangover this morning! Goin' away beach party last night.........:faint:

Hmmmm, Beach Party hu??? Been to a few of those I must say . Know how it goes.. I fell into many bottles of tequillia and drank my way out... HEHE!!!
Ill see if I can pick up a kit you speak of...
Where do you live? Im in Fort Lauderdale, FL

Thanks,

Ant...:joyous:

 

[Dukedog]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

Retired. We're just travlin' tha country. Just left Pensacola Beach Yesterday. Workin' our way ta Phoenix and Havasu boat races............

 

[Ant-Knee]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

I think the module is the culprit,
I disconnected the temp sensors to eliminate them , And alarm still sounds off.. ( So its Not the temp sensors.
I also diconnected the motion sensor and it still sounded off..
When I dis connect the module it shuts off...

Does this mean the module has seen better days?

Thanks,

Ant...
'

 

[CharlieB]

Re: Help Please!!! 1998 Merc 150 overheat alarm will not go off, But not over heating

Without the auto oiler you do not need the module or the oil pump. The 'kit' they mentioned it used to remove the pump and fill the 'empty' space.