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Author Topic:   Engine Temperature Gauge Wiring
70mack posted 07-04-2008 12:51 PM ET (US)   Profile for 70mack   Send Email to 70mack  
[Give me] tips on installing a FARIA temperature guage on my Yamaha 90-HP outboard. All I received in the kit were the guage and sending unit. I need advice on the installation of the sending unit and wiring. Thanks--70mack
Joninnj posted 07-05-2008 07:35 AM ET (US)     Profile for Joninnj  Send Email to Joninnj     
Hello. I am about to do the same thing on a 90 HP Yamaha. I do not think it is difficult. Just a question of adding or replacing the sensor. There is one in the engine already as it does have an over heat alarm.

Good luck

jimh posted 07-08-2008 12:22 AM ET (US)     Profile for jimh  Send Email to jimh     
Electric temperature gauges usually need only a single wire run from the gauge to the engine sensor or sender. The engine sensor or sender is usually mounted in a pre-formed and threaded boss on the cylinder head of the highest cylinder (because it will be the hottest). The engine block provides the ground path. Usually a thread compound is applied to insure good heat transfer.

Of course, the gauge itself will need to be supplied with the igntion-key-switch 12-volt source and ground, as well as an illumination circuit. For help identifying the wiring by color code, see

The existing sensor used for the overheat alarm in most cases is just a simple thermostatically operated switch, and it is not in any way useful for a temperature gauge sender or sensor.

swist posted 07-09-2008 08:58 AM ET (US)     Profile for swist  Send Email to swist     
I'm pretty sure the sensors are not universal across brands, so I'm assuming you bought the gauge with the sensor for that engine. Then it's just a simple matter of poking around the block finding the blank for it. I believe that all outboards over a certain size have provisions for temperature sensors, whether or not they came with one to begin with.
timing posted 07-09-2008 11:11 PM ET (US)     Profile for timing    
I’m an advocate of having both water temp and water pressure gauges, and have installed them on nearly all of my outboard powered boats for more years then I want to admit. Have added Faria gauges to my current Outrage - Yamaha OX66 200HP engine.
Some DIYer install notes –
Never consider using an oem temp sensor even if it could work with your gauge, leave that AUDIBLE system in place and add your temp gauge as an additional system.
If you lucky enough to find an existing port in the head which the gauge’s sensor threads into, good for you. I’ve never found this to be the case with aftermarkets, and use the supplied elongated oval / rectangular mounting bracket with 2 holes. One hole to mount the bracket, and the other a threaded hole for the sending unit. Goal is to mount the sending unit on the upper portion of the head, perpendicular to the head surface, where threading the sensor through the bracket allows it’s tip to rest flush against the head surface. This interface can’t be overstated, and I’ve had success in using a thermal compound to facilitate heat flow from the head to the sensor. Thermalcote - We’ve used this compound to heatsink industrial PCB devices, and it also works fine on outboard temp sensors. In terms of mounting the bracket to the engine, I prefer to not disrupt sealing bolts (ie head bolts), and seek a mounting bolt of some type. On my current install, I couldn’t find a non-sealing bolt at the top of the head and ended off bonding it with marine tex. Held the bracket in place perfectly, but electrical isolation then required a ground strap from the sensor’s outer housing to an engine block ground. And for the wire’s slide on terminal to sensor connection - like all electrical connections that can be seen, cover/seal it with dielectric grease.
Last year my temp gauge came through in letting me know I had a slight increase in operating temp. Turned out to be slightly corroded thermostats which I was able to replace before any alarm / issues occurred.

jimh posted 07-10-2008 12:03 AM ET (US)     Profile for jimh  Send Email to jimh     
On my 1992 OMC V6 engine there are two prepared threaded bosses, one on each cylinder bank, intended for the installation of electrical sensors for temperature gauges.

In a prior discussion on precisely this topic, I included a photograph showing the treaded-in temperature gauge sender. Compare at:

Wiring a Temperature Gauge

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