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1977 70HP operating Temp

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rude70

Contributing Member
I am trying to calibrate a sen

I am trying to calibrate a sender unit to an OMC temp guage. The sender unit is mounted to touch the cylinder head. Does anone know the normal operating temperature of a 1977 70HP?

Thanks
 
It should be about 160F on low

It should be about 160F on low idle. However You should experience a DROP in temp almost to 140 at around 3/4 throttle/load.
 
The thermostat in your engine

The thermostat in your engine is 143 deg so at idle it will be around this temp...when you put the throttle down around 2300rpm the water pump pressure blows the bypass valve off its seat and cold water flows through the engine.
 
"Thanks, I tested the existing

"Thanks, I tested the existing stat using a pot of water on the stove an a thermometer and it began to open at around 165degrees. I bought a new sierra stat that stated 143degress on the packet & on the stat - it also opens at around 165degrees. Is this normal?

Thanks"
 
Yes. Se my reply above. To my

Yes. Se my reply above. To my experience that has been the reading I have obtained on most of the T-stats even if nominal temp is 143.
 
"Thanks, I did your reply abov

"Thanks, I did your reply above. It is pretty confusing since the OMC temp gauge from my tests is half way at 143 degrees and just touches red at about 175/180. So how confusing is that!!

Regards"
 
Not sure yet since I am finish

Not sure yet since I am finishing a complete rebuild. It will be a couple of weeks before I finish
 
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