Mercruiser 5.7 carb Warning signal temperature

Hello!
I bought a used boat Wellcraft Eclipse 20 Mercruiser 5.7 carb. (# OK178561). I think it's a Mercruiser 350 MAG. ALPHA (4 BBL.) GM 350 V-8 1997. I haven't other engine numbers. Cover on carburetor does not here (write "OMC cobra").


The previous owner made a change in the motor. The wires do not coincide with the wiring diagram.
If I have correctly identified the motor, the sensor alarms must be single ended (second contact - ground).



I see a temperature sensor and oil pressure with two contacts. Ordered with 1 contact can not be install:




Does anyone help me to understand the wiring or motor model? I need it to deal with overheating or temp sensor.


I have and described the problem in another old thread: warning signal when planing. I found that guilty the temperature sensor. The engine temperature is not increasing (160-170). The engine speed is 3000 - signal appears. If run up to 4000 - the signal disappears after a few seconds. Reduced to 3000 - appears again. If lightly touching the throttle lever - signal may disappears instantly. At 2800 - no signal. At idle to.
Thermostat & gasket changed (OEM). Water pump replaced in the spring(OEM). Exhaust manifolds are not too hot - do not burn the hand. Oil in the engine clean without water. Clean lakes water last 10 years. Changed poppet valve.




I asked: will it help if I replaced the temperature sensor?
There was one response: No. Check connectors Ignition Control Module.
Thank's boat_tech for answer! I'll try to check the connectors Ignition Control Module at the weekend. Gasket thermostat I changed 2 weeks ago on a new OEM.
I noticed that the alarm depends on the trim of the boat. Lifting / lowering trim nose affects the appearance of the signal.
The signal appears when the boat comes on plane after 1-10 minutes. If I change a little-little throttle control - the sound immediately disappear, but may reappear. This is very similar to a bad contact! It remains a bit: only to find it...
And I hope that the problem is in the contacts.


Ok, it may have other ideas?
I would be glad of any help.

the sensor in the pic might be the oil pressure switch for the electric fuel pump

No, both the temperature sensor from warning system. New (photo) is #806951, "Was installed" (photo) with two pins is #805218T.
I found pn#805218T in the scheme of engine parts Mercruiser 5.7L (2 BBL.) GM 350 V-8 1998-2001.
For oil look like this:

I changed it to.

It's an odd issue you seem to be having possibly due to a mismatched engine combination of parts.

The sensor you removed from the thermostat housing, Did the sensor have Yellow and Black wires connected to it mounted to the port side of the boat/Engine (< facing the bow of boat, not the engine) or a single Tan/Blue wire to it?

The parts diagram shows it should be the single Tan/Blue designed wire for the warning horn switch from new... But you removed the Yellow & Black wire designed switch which would be OEM part number 805218T seen in the image below indicating mismatched parts vs OEM part number 48952 that looks like this in the following link, http://www.ebay.com/itm/Mercruiser-...ash=item2eddde608d:g:h3EAAOSwPYZU5Jkp&vxp=mtr

My original post to you was just something different to try doing to see if maybe it would help at all believing you had a newer engine model like the guy in the older topic you brought back up which I wasn't replying to due to the topics age... Your situation if completely different now so disregard my other post to you.... I should have know better than that by now...

Qty Required For Repair: 1
Minimum Order Qty: 1

Thanks to the clever American who made a different thread on the sensors! This is the "protection of the idiot"!
I could not screw the sensor from the old model and all back into place like it was!
Now the sensor is installed on both your photos. I have not replaced it. Yellow and black wires connected to it. Sensor at left (port) side of the boat:




I'm not very good at English, I'm sorry. That's right, I understood, that I must to replace the sensor at the same new?
It's easier than digging in contacts!
Many Thanks for your attention to my problem!

Hello!
Today I received the sensor and installed it.




After that I tested the boat. The problem is not in the sensor.
The alarm continues. Oil sensor off. I made a video. Maybe this will help?


Thanks in advance for helping me!

Looks like the gage head (that is doing the measuring, is off a bit or too sensitive. If you move the sender unit away from the motor with a pipe extension, you might get it to work properly.

Jeff

I think It's a good idea! I'll do if I can not find mulfunction. I want to understand why the sensor is triggered so close to normal temperature. In the video, on gauge 170F temperature. Thermostat installed 160F.
Normally, that the temperature is higher than 160?
Must sensor operate on the 170 or higher?

Does the problem seem to go away when you disconnect the Yellow / Black wiring connector while running the boat at speed?

Did you happen to try disconnecting the wiring harness at the Ignition Control Module to see if it helped any?

Try with the engine running, wiggle the main wiring harness cannon plug connector at the engine to see if the horn will sound also find the Tan/Blue wire and trace them wires between dash to the engine the best you can with the engine on to see if the horn beeps at all while carefully wiggling the wire around. http://www.iboats.com/Mercury-Marin...ine-Harness-CDI-Electronics/dm/view_id.335995

In some cases, it is not to usual to see a 170ish temp reading on the gauge knowing a 160-163 degree thermostat is installed and the engine is not actually overheating.

Thanks for the answer!
Now I will move the wires and test sockets.
I don't like the temperature gap between thermostat and gauge 160-170. I can not be sure that the engine does not overheat. But above 170 is not growing. Only sometimes, when I stop the engine for a two minutes and turn on again. It signals a few seconds until it will pump fresh water cooling system. I think this is normal.
The most difficult thing that I don't have a suitable wiring diagram. One could see the signals on the wires from the sensor to the engine connector. I don't know where the yellow/black wire goes into tan/blue.

RAW water cooled engines , i.e., engine and manifolds directly cooled by the water the boat runs in, running in salt water have 140 or thereabouts thermostats and a 170 degree alarm would be about right for those engines, while engines with a heat exchanger run a 160 degree ( or thereabouts) thermostats. I would expect the alarm set for the sensor in this case to be closer to 190-195 degrees.

From what I am seeing the two wire temp senser is for the ECU there should also be a 1 wire sender for the temp guage. The warning signal is a low oil alarm and will sound until oil pressure comes up. Does the alarm stay off while the engine is running? I think your looking at the wrong issue this is a throttle body injected motor correct?

http://www.marineengine.com/parts/m...997/0k001506-thru-0k999999/wiring-harness-efi
http://www.marineengine.com/parts/m.../0k001506-thru-0k999999/wiring-harness-engine

The alarm will sound with both low oil pressure or low oil level in the drive.

kimcrwbr1 said:

This is a throttle body injected motor correct?

Click to expand...

The OP (Andrey) has a carbureted engine model.
1997 5.7L model number 457B100KS MERCRUISER T.B-5, W/PS, TWO-PC-EX, WORO 5.7L ALPHA Drive.

Here's his parts catalog if needed, http://www.marineengine.com/parts/mercury_marine_parts/sn/0K178561

The engine temp warning horn is sent via the sensor with the Yellow/Black wires to the Thunderbolt 5 ICM first before going to the warning horn...The two oil systems go directly to the warning horn via the Tan/Blue wire.

Did you have a chance to watch the video yet? > https://youtu.be/_eZPEmHQEOE

Sandkicker, the last temp setting to sound the warning horn that I recall for these engine models is 196 degrees.

Thanks to all responded!
Yes, I have a carbureted engine with water cooling.
The alarm stay off while the engine is running at idle, low (1000-2700) and high (4000) RPM. From 2800 to 3500 - I hear the warning signal.
Sometimes quite a bit to move the throttle control - the sound disappears. Or increase the engine speed to 4000 - disappear too.

The previous owner of the boat changed something.
I have two wires from alarm temperature sensor (yellow/black), and two wires from the sensor alarm oil pressure:



All wires go to the ICM.

These sensors are not suitable
http://www.marineengine.com/parts/mercury_marine_parts/sn/0K178561/457B100KS/1939_350 - both for one wire.

The level of transmission oil through the tan / blue wire to the warning horn immediately.


I cut off one by one sensors and found that the problem is in the temperature.
If the temp setting to warning is 196 degrees, the problem another then overheating.

If the problem is in сontacts, the temperature sensor is disconnected or not - should not affect the signal? Because shorting somewhere upstream circuit. I think, I need to connect an ohmmeter to the sensor temperature and see its signal. If the signal changes on the sensor - I will seek to overheat.
If the signal does not change and warning signal is ON, then ICM or contacts.

Scold my idea.....

boat_tech said:

The OP (Andrey) has a carbureted engine model.
1997 5.7L model number 457B100KS MERCRUISER T.B-5, W/PS, TWO-PC-EX, WORO 5.7L ALPHA Drive.

Here's his parts catalog if needed, http://www.marineengine.com/parts/mercury_marine_parts/sn/0K178561

The engine temp warning horn is sent via the sensor with the Yellow/Black wires to the Thunderbolt 5 ICM first before going to the warning horn...The two oil systems go directly to the warning horn via the Tan/Blue wire.

Did you have a chance to watch the video yet? > https://youtu.be/_eZPEmHQEOE

Sandkicker, the last temp setting to sound the warning horn that I recall for these engine models is 196 degrees.

Click to expand...

The purple and purple/yellow wires are for powering up an electronic fuel pump which your engine serial number suggests you do not have from new however someone has changed what seem to be a lot of parts over to a newer engine design model. So it's hard to tell exactly what you have there.

Do you know if you have a mechanical fuel pump or an electric fuel pump?
Here's what your Mechanical fuel pump would look like using your engine serial number, item number 1, http://www.marineengine.com/parts/mercury_marine_parts/sn/0K178561/457B100KS/1939_60
Item number 2 would be an electric fuel pump, http://www.marineengine.com/parts/m...10037-thru-0m599999/fuel-pump-and-fuel-filter

Since you know the engine is not overheating + you have already replaced the temp sensor unit, you installed a new OEM base thermostat housing gasket with the brass rivets (Dry? = with no sealant added to gasket?) which is needed to help complete a good ground path for the sensor, Found the warning horn to stop sounding with temp sensor disconnected..... About the only 4 things left is the wiring between the sensor to the ICM is affected, the ICM needs a good ground wire to the Ignition Control Module "Casing", one of the wiring pins or plug connectors is compromised, Or some sort of internal issue inside the Thunderbolt 5 Ignition Control Module itself. < That's one of the reasons I recommended removing all of the ICM plug connectors, inspect and clean them and then retest the boat to see if it helped at all. Ohms testing between the Yellow (& Black to ground) wire to the ICM would be a good idea as well just to see their overall condition.

Yes, I think that the previous owner replaced the wiring and may be something else of the later model.
I saw somewhere in the later models such oil pressure switch with 2 pins. He called the Oil Pressure Sensor Switch:


I have the same sensor oil pressure.


I have an electric fuel pump, you have indicated the number 2.
My ICM look like this:

https://www.marineengine.com/newparts/part_details.php?pnum=MER861254T02


I installed the original gasket thermostat without sealant (Thanks to the forum!) and clean the surface with sandpaper.
I even replaced with a new the Terminal Block, that there was no doubt about the ground:



If I have time before the frost, I will check the boat on the water. If not - I will clean all contacts. Check with ohmmeter ground, wires and connectors. Winterizing and will wait for spring with a nightmare in my head and with hope in my heart.
A huge thank to everyone who helped and was interested in my problem. If there are good ideas - I will be glad to hear.
Be sure to write what was the reason that'll fix the boat.

Perhaps, it will be interesting and important to someone. I cleaned the contacts of the IСM with liquid to clean the contacts, and the problem with the overheating signal disappeared. About 3 hours of travel by boat in different modes - everything is OK! Thanks to everyone who responded to my problem!