Engine Temp Sensor Location & information

KnotConnected

Petty Officer 1st Class
Joined
Aug 15, 2012
Messages
221
Hey!

I've been reading horror stories of the damage caused by over heating, and want to make sure I can avoid the same issues. I've been studying the cooling system in the manual (Merc's #16 for the 1994 454 B-III) but don't see any mention on where the temp sensor is in the system or see anything in the manual about it.


Questions
1) If the intake gets clogged and the open cooling system is WITHOUT water, will the temp gauge show overheating if there is no water in the cooling system?

2) if the impeller fails, I assume water remains in the cooling system, and overheating will be evident on the gauge, correct?

3) there IS a thermostat in this system, and i should find it and replace it anally as i would in a car, correct?

4) Is there an audible alarm on these older engines for something like heat issues? If not, is this kind of thing commonly added to the system for just-in-case?


Thanks again to all!
 
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Bondo

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Staff member
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Apr 17, 2002
Messages
70,465
Re: Engine Temp Sensor Location & information

Hey!

I've been reading horror stories of the damage caused by over heating, and want to make sure I can avoid the same issues. I've been studying the cooling system in the manual (Merc's #16 for the 1994 454 B-III) but don't see any mention on where the temp sensor is in the system or see anything in the manual about it.


Questions
1) If the intake gets clogged and the open cooling system is WITHOUT water, will the temp gauge show overheating if there is no water in the cooling system?

2) if the impeller fails, I assume water remains in the cooling system, and overheating will be evident on the gauge, correct?

3) there IS a thermostat in this system, and i should find it and replace it anally as i would in a car, correct?

4) Is there an audible alarm on these older engines for something like heat issues? If not, is this kind of thing commonly added to the system for just-in-case?


Thanks again to all!

Ayuh,.... #1,.. If the motor was drained dry, 'n started without water, the gauge would show Nothing,...
It reads water temp, not air temp,...

#2,... Ya, a runnin' motor has it's water, so it would show an overheat due to lack of flow,...

#3,... There's Supposed to be a t-stat, inside the t-stat housin',...
When ya service it is yer choice,... not sure you'd wanta sit on it though,...

#4,... There may, or may not be a temp switch near the temp sender, usually found in the t-stat housin',...
I'd think, the buzzer would be under the dash,.....
Both can easily be added,...
 

KnotConnected

Petty Officer 1st Class
Joined
Aug 15, 2012
Messages
221
Re: Engine Temp Sensor Location & information

Thanks Bondo, you're a stud!
 

agallant80

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Oct 25, 2010
Messages
2,328
Re: Engine Temp Sensor Location & information

From what I understand you should be covered. If say the t-stat gives way there would still be water in the block hearing up the motor and the temp sensor. If the impeller gives way or a plastic bag gets sucked up the no/low water pressure sensor will sound the alarm.

Bondo,

Does that sound correct?
 

Fishermark

Vice Admiral
Joined
Oct 19, 2003
Messages
5,617
Re: Engine Temp Sensor Location & information

#3,... There's Supposed to be a t-stat, inside the t-stat housin',...
When ya service it is yer choice,... not sure you'd wanta sit on it though,...

You're a bad man bondo! ;) Me-thinks it be a typo. :D
 

tpenfield

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Staff member
Joined
Jul 18, 2011
Messages
17,621
Re: Engine Temp Sensor Location & information

Hey!

I've been reading horror stories of the damage caused by over heating, and want to make sure I can avoid the same issues. I've been studying the cooling system in the manual (Merc's #16 for the 1994 454 B-III) but don't see any mention on where the temp sensor is in the system or see anything in the manual about it.


Questions
1) If the intake gets clogged and the open cooling system is WITHOUT water, will the temp gauge show overheating if there is no water in the cooling system?

2) if the impeller fails, I assume water remains in the cooling system, and overheating will be evident on the gauge, correct?

3) there IS a thermostat in this system, and i should find it and replace it anally as i would in a car, correct?

4) Is there an audible alarm on these older engines for something like heat issues? If not, is this kind of thing commonly added to the system for just-in-case?


Thanks again to all!

Just to add to the answers already provided . . . I know the answer to #1 & #2 from direct experience :facepalm:

1) In the scenario where your engine is suddenly deprived of water . . . Yes . . . the temp gauge will climb quite rapidly (from my experience, until the alarm buzzer goes off and smoke starts coming out from the engine compartment). In the scenario where your engine block is completely drained, the temp gauge won't register the heat as quickly as there is not water in the engine block.

2) yes, as described above . . . no additional water will be introduced to the engine and no water will leave the engine and go out the exhaust. the exhaust tends to get hotter sooner than the engine, but in my experience it was all within 15-20 seconds.

3) Yes should have a thermostat, if it ain't broke . . . don't fix it.

4) My 1991 454 B1 had an audible alarm and it did work when the intake hose blew off the sea water pump (and the engine over heated). So, it would be reasonable that a 1994 would have the same or better. Check under the instrument panel for the little buzzer to verify. . . or alternatively look at the thermostat housing and there should be 2 senders . . . one for the gauge and one for the alarm.
 
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Fun Times

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8,776
Re: Engine Temp Sensor Location & information

If the impeller gives way or a plastic bag gets sucked up the no/low water pressure sensor will sound the alarm.
Only the engine models that have the 555 ECM, PCM and newer model control units (2001 +) will have the "low water pressure" sensor as standard equipment from Merc. The mefi ecm's (2000 -) did not offer "water pressure" sensors. They only offered water temp and warning horn switch.

Carbureted engine models in 94 would have had/offered water temp and warning horn switch as standard equipment. The only engine model in and around 1994 that I can think of that had the warning horn as an option was the 3.0L while the 3.0LX offered the warning horn as standard.

The warning horn looks to have started in 1989, http://media.channelblade.com/EProWebsiteMedia/3506/Mercruiser warning horns.pdf
 
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