Fitting a temperature gauge 1991 200 Hp Mariner

[Keithm18]

Hi guys. I need your help again please.

In reading my manual i have found that my motor should be fitted with a temperature reading unit that will enable me to fit a temperature gauge.

As I understand it on the Port (Left) head of the motor there is a two wire sensor with a plain tan wire that should be connected to the overheat horn and the black one earthed on the head.
On the Starboard side (right) is a sensor with only a single wire which is tan with a blue stripe that runs into the harness.

In the front at the remote I have found that the tan wire with the blue stripe is not connected to anything.

Here's my question. the wiring diagram in my manual shows that the tan wire should go into the temperature gauge and is also says the tan wire should go the warning horn, but says nothing about where the tan and blue wire should be going...

So I have a few questions.

Which head is wired to the overheat warning horn in the remote? are they both through some kind of splice in the harness?
Which wire can I connect to the temperature gauge to read the effective head temperature? the blue and tan or just the tan wire?
Should the blue and tan be connected to anything?

Lastly can I connect a normal Automotive electrical temperature gauge to the correct wire from the sensor in the motor, or do I have to get a specific gauge at $70 plus?

As always thanks for the help.

 

[galamb]

You have it correct.

The starboard head (right side if you are behind the motor) has the temperature "sensor" that feeds a temp gauge. It has a tan wire (single wire) connected to it. It will run along with the harness up to the front of the boat BUT it's not part of the harness plug itself - will run along with the trim/tilt wires etc and the harness wires up to the front.

The tan/blue wire from the water temperature sensor is included as part of the harness (pin 3 on your model I think). It feeds up to the front BUT unless you have a visual warning aid of some kind (overtemp light etc) it will normally just be taped off at the instrument cluster.

So to your questions.

The "sensor" on the port head (with the two wires) is the one wired to the alarm module on the motor itself. It should send a black wire back to a little connector block that gets the wire from the sensor plus two (2) tan/blue wires (one goes off to the alarm, the other heads to the harness connector) and two (2) purple wires (again, one to the alarm module and one off to the harness).

The "sender" on the starboard head has a single tan wire that heads right up to the front of the boat. It has a bullet connector located at the same length as where the harness plug is on the motor side of the harness connection. Again, it kinda piggy backs with the harness wiring up to the front.

The sender is a simple resistance type unit so any temp gauge that simply measures the resistance to determine the temp will work fine.

As someone mentioned here recently. OMC senders and gauges are waaaaaayyyyyy cheaper than most Merc products. The sender just screws in to any convenient location on the block (so doesn't even have to be specific to Merc, never mind model)...