SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

[dogsdad]

I'd like to know the readings folks have gotten when measuring the cylinder head temperatures with a laser/IR thermometer.<br /><br />My motor is a 1991 135-Horse Mercury Black Max. I have been questioning the reliability of my temp gauge on the dash, so I took a reading the other day. I ran the motor at idle for a reading, and at 3000 rpm, prop engaged, for a couple of minutes to warm it up for another reading. This was done in the driveway, on muffs.<br /><br />At idle, cylinder head temps were right at 150 degrees. At 3000 rpm, I got a high reading of 174 degrees.<br /><br />I'd like to know what anyone else has seen, and if 174 degrees seems to high at light load. Please state what your motor is and what readings you have gotten.<br /><br />Thanks all!<br /><br />-dd-

 

[Mercury140-I6]

Re: SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

Hello:<br /><br />I don't know about the temps, but it's a VERY BAD idea to run these motors on muffs over 1800 RPM's under and conditions. It ca do serious damage to the motor.<br /><br />Craig

 

[BillP]

Re: SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

Mercury140-I6,<br />Not to hijack the thread but what type of damage will happen if running 1800 rpms in neutral on water muffs?

 

[Merc805]

Re: SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

The manual says not to exceed 1200RPM. My guess would be that there is no load on the motor and not enough flow from a hose/muff setup.

 

[Hooty]

Re: SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

I'll talk with ya about temps.<br />You're right, that 174* sounds high. How did it compare with the your temp gauge? Were you reading the infrared temp at the gauge sending unit? <br /><br />c/6<br />Hooty

 

[Mercury140-I6]

Re: SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

BillP:<br /><br />I have heard it from Clams Camino, who is a mechanic. Other than a possibility of run away, I personally don't know.<br /><br />Craig

 

[rickdb1boat]

Re: SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

Could be the muffs didn't supply enough water properly to get correct readings. I'd try it again when in the water or a tub of water. 160* would be about right...

 

[Clams Canino]

Re: SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

It's not so much runaway (though that's a risk) it's "parts float" to worry about. These things were designed to run under a load and it's part of the kinetic "geometry" as it were. I consider 1500 a safe warmup and 2000 the max "oops".<br /><br />I don't know how many of us have(or carry) a Laser-Infra red Thermometer by the way.<br /><br />-W<br /><br />

Originally posted by Mercury140-I6:<br />BillP:<br /><br />I have heard it from Clams Camino, who is a mechanic. Other than a possibility of run away, I personally don't know.<br /><br />Craig

 

[KCLOST]

Re: SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

Dogsdad,<br /><br />Just to clear something up that Hooty mentioned. Remember that your temp sensor (I believe) is measuring metal temp. Not Water temp. Your temp guage at the dash will normally read much higher temps than what the water temp will be. They won't necessarily be the same. You can confirm what the temp sensor is measuring by removing the bracket that holds it in place and see if it ever enters the water jacket. I bet it never does and is touching metal on the cylinder head.<br />What concerns me, is that your measurements do seem a bit high, and depending on where you are pointing the lazer, you most likely are measuring metal that has water flowing just underneath. What readings are you getting on the guage, just for clarity?

 

[jim dozier]

Re: SURVEY: Cylinder Head Temps Taken w/Laser-Infra Red Thermometer

Remember that cylinder heads run hotter than the block. I think most manufacturers recommend checking "engine" temperatures on the block between the flywheel and the cylinder head. I think around 163 degrees F is max normal for the block, and it would be higher than that for the cylinder head (metal, not water). So 174 degrees F. for the cylinder head metal may not be too high.