'91 Merc 115 HP Temp Gauge

[MiBad]

I would like to install a temp gauge on my 91 Merc 115 HP. I already have the water pump connected and I am in the process of picking up the wiring harness for the Commander 2000 control for wiring the gauge (as well as the temp gauge). Does anyone know for sure if the temp sending unit is already installed in the motor (which in turn will be wired to the wiring harness)? If not, does anyone know where the sending unit should be connected? I am already using the port located above the #1 cylinder for the water pressure gauge, and the over temp alarm sender is already wired into the standard location.
Thanks in advance.

 

[Texasmark]

The temp sending unit that is already installed (factory OEM) is the over temp alarm sensor. It is easy to find as it has a tan or tan with light blue stripe coming out of it and is located on the same plate where you mounted your water pressure gauge, just to the left and down on the other side . Other than that, don't know of any more holes unless you drill and tap your own. If you do, and I have done it on another engine, just remember that you need to get off to the side, like these holes are located because the cylinder and head are under the majority of the center of the plate.

 

[MiBad]

Thanks for the info Texasmark. I thought I read somewhere that a temp sensor was pre-wired to the controls, but I must have misunderstood. They might have been talking about the over temp alarm sensor that you mentioned. As it turned out, after I got the wiring diagram with the harness I found that there was no mention of wiring for a temp sensor - only the over temp alarm, the tach, and a trim gauge. The additional gauges still come in handy. If I find a good place to add the temp sending unit I'll post it.

 

[Texasmark]

Thanks for the info Texasmark. I thought I read somewhere that a temp sensor was pre-wired to the controls, but I must have misunderstood. They might have been talking about the over temp alarm sensor that you mentioned. As it turned out, after I got the wiring diagram with the harness I found that there was no mention of wiring for a temp sensor - only the over temp alarm, the tach, and a trim gauge. The additional gauges still come in handy. If I find a good place to add the temp sending unit I'll post it.

On my last Commander 3000 (the one with the big black button for throttle only) which was installed in the boat when I bought it, the wiring was there for the OT monitor....tan/lt. blue stripe. It was a loose wire clamped to the harness near the control box. This wire is provided as some boats have 2 methods of alerting someone that the engine is over heating. One is the horn and that second wire is for a light which on one boat I saw is mounted in the dash in front of the operator. Good idea for when there is a lot of background noise in the boat and the operator may not hear the horn. Not an analog readout and nowhere have I seen such a wire in the OEM wiring harnesses for the engines or the Commander 2000 or 3000 controls.