What is the Temperature of a running 70hp?

[onehunglow]

I want to install a temperature gauge on my Evinrude 70hp - I purchased the OMC temperature sensor and it screws into a threaded hole on the cylinder head, not far from the temperature hot warning sensor.

When I plugged in the OMC temperature gauge (which shows 120-220 degrees), the needle on warmed-up idling shows 200 degrees - near the very top end of the scale! It would be hard to see an overheat condition since the the gauge seems to be "maxed out" to start with.

However, plugging in a Faria temp gauge 100-250, the 200 is not at the top, but more like 3/4's

Now I understand that there are gauges that are made for water temperatures and those made for cylinder head temps. Mine is the latter.

Is what I am seeing normal?

 

[gyoung]

Re: What is the Temperature of a running 70hp?

Onehung,

I installed a Faria temp sensor on my 1985 70hp. The thermostat is supposed to open at 140 degrees. My gauge reads about 135. The 5-degree lose is probably due to temperature gradient across the water jacket and the less-than-perfect contact one can get with the external sensor.

I installed it on the flat spot on top of the head just behind the lift hook. I replaced one of the lift hook bolts with a longer one to anchor the sensor.

Your engine is either overheating or the gauge is faulty. Or possibly the supply voltage is too high. You should get close to 140 after idling for about 5 minutes. The tempurature on mine actually decreases a few degrees after it's opened up to WOT because the pressure relief valves open to let more water through.

GY

 

[tashasdaddy]

Re: What is the Temperature of a running 70hp?

agree

 

[onehunglow]

Re: What is the Temperature of a running 70hp?

Yup- that makes perfect sense

But it could also be a faulty sensor!

Anyone know what the ohms between the S and Ground should be for 140 degrees?

 

[Silvertip]

Re: What is the Temperature of a running 70hp?

Water Temp Sender (100 - 250 gauge)
100 Deg = 450 ohms
175 Deg = 99 ohms
250 Deg = 29.6 ohms

Cylinder Head Temp Gauge (60 - 220 gauge)
60 Deg = 1195 ohms
140 Deg = 192 ohms
220 Deg = 46 ohms

 

[onehunglow]

Re: What is the Temperature of a running 70hp?

AWESOME information - this must be posted in an important place!

Logically, there is no way my engine can be running at 200 degrees since the water coming out of the pisser would be extremely hot (actually burning) which is not the case.

I strongly suspect a faulty sensor.

I am going to order a new sensor - do you know the # or can you direct me to find the part# of a cylinder head temp sensor for an OMC (Evinrude specifically) 70hp circa 1987 ?