water temp gauge

[canman]

hi everyone , i just installed a water temp gauge in my 1990 johnson 140 . when it is idoling or going real slow the needle on the gauge will go about half way , just as soon as i start to give it more gas to go faster the needle will drop back down to the bottom of the gauge . is this the way this gauge is supposed to work ? i have the screw in sensor . pretty easy to hook up . thankyou .

 

[Silvertip]

Re: water temp gauge

I will assume you have a gauge that is calibrated C - N - H. If that's the case, middle of the gauge is normal. At idle the bypass valve is closed so engine temp is controlled by the thermostat. As engine speed increases, the bypass valve opens so it is very normal for the engine to cool down during high speed operation. You should have now determined that if the engine reads hot at idle but cools down at speed, it's likely a thermostat stuck shut. If the engine runs normal at idle but overheats at speed, then the bypass valve is likely stuck closed. If the engine stays cold all the time, the bypass valve and perhaps the thermostat as well are stuck open.

 

[canman]

Re: water temp gauge

when i installed the sensor i wrapped teflon tape around the threads of the sensor . would this have any effect on the sensor ? thankyou .

 

[ezeke]

Re: water temp gauge

No tape. The instructions should have come with the kit. You need a solid electronic ground and thermal connection for the sensor to function properly.

As far as the reading, the 1988-1992 140 90 degree Loopers had an unusual thermostat setup. The temperature reads high at idle because it is.

 

[canman]

Re: water temp gauge

i will take the tape of the sensor tomorrow and reinstall the sensor and see if that makes any difference . the motor is a fresh rebuild that i bought last month . i would think they would have checked the thermastats. thankyou.