Adding a Temperature Gauge

[Prof T]

Hello...new to the forum

I would like to add a dash temperature gauge to a 2016 Crestliner Commander, non Smartcraft 2016 Mercury 90 Fourstroke, Model ME90XL45. Motor has a sender near the thermostat housing that I assume is connected to the Guardian engine control system.

System functions correctly as I had an overheat problem that has been corrected. I would loose cooling flow at RPMs over 5000 (WOT). Impellor teardown showed the cup washer on the driveshaft that fits down against the top of the pump housing was cracked and laying loose in the housing. Not the greatest design in my opinion.

Anyway, I want to install a regular temp gauge so I can monitor conditions. Is there a way to use the same sensor and is the wiring already included in the harness? Can anyone point me to a schematic for this engine/setup.

Thanks in advance
Prof T

 

[alldodge]

This is a woops on my part, thought you started 2 threads of same post but you posted to an old thread and then this one

Gauge is pretty simple, Connect sender to sender connection on gauge.
Connect 12V and ground to gauge connections and its done.
Do use a 12V connection that is switched ON when key is turned to ON

 

[Prof T]

Will there be an existing lead from the sender at the dash end of the harness or will I need to splice into it at the power head and run a new line?

 

[alldodge]

Being a Merc look for a Tan colored wire, if not there will need to add one. The typical 10 pin harness has all the wires listed

 

[Prof T]

Thanks, exactly what I was looking for.
Cheers

 

[Chris1956]

Be aware that temp gauge senders are different than overheat sensors. I expect the sensor connected to the guardian system is the latter.

Overheat sensors will not power a temp gauge as they are open or grounded, whereas a temp gauge sender has variable resistance to ground, based upon the motor temp.

Lots of Merc V6 motors have both kinds of sensors, one on each head. Not sure what you have.

 

[froggy1150]

Pull a sensor. Attach a meter on it set to ohms and drop in 200 deg water. If the reading changes icrmentally in a numerical value it should work on temp guage. If it switches from close to open to close it's just for a id10t light. Also note the resistance range to order the right guage if it operates like the first example

 

[Prof T]

Updated:

Mercury keeps their shop/repair manuals pretty well hidden on the web so I went off and purchased one. I plan to have the motor a long time and spent a career as an Industrial Arts teacher, so I like to do as much of my own repair work as possible.

The sender is mounted right by the thermostat and has two wires: tan/black and black/orange. The black/orange leads to a common ground for all of the sensor wires (ECM PIN 42). You can test the sensor by disconnecting its plug and checking with an ohm meter between the two wires.

32 degrees - resistance should be very high (32.6 k ohms)

77 degrees - room temperature (10 k ohms)

122 degrees - area where my last motor liked to run in cold water - (3.6 k ohms)

212 degrees -OVERHEAT - 678 ohms

Sensor is very much like an automotive sensor, a wet probe into the water jacket.

It appears to me that I can use that probe and wiring to a traditional gauge like I wanted to. Shrink wrap comes off today, I’ll keep the wrench heads out there posted.

 

[alldodge]

With the resistance readings shown you must be on the other side of the pond. North American standard is 240 cold , 33 hot

 

[Scott Danforth]

Updated:

Mercury keeps their shop/repair manuals pretty well hidden on the web

Manuals are copyright material. Only available for purchase from your local dealer or from http://publications.brunswick.com/

Any PDF copy claimed is most likely a scam or phishing site