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Checking Engine Temp using Digital thermometer


shanson

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I read this REALLY good article in Practical Boat Owner (my fav rag) about how to check your engine using a digital laser thermometer.

 

I went out and brought on but can't find the article. It has some really good stuff, like what temperature your stern gland should be.

 

Does anyone know which edition it's in? I've searched their website with no joy.

 

Cheers

 

SHANE

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I remember it and it must have been from sometime back. I can't look it up as last week I dumped 10 years worth of mags I had in storage.

Don't get overly excited about the temp thing Shane. I think that article got written by a "kid with a new toy". For example, a regular Stern glands need to drip water. 3 -5 drops a minuite is about right. Gortex packing can be run dry and you simply tighten just till the water stops. Dripless should not get warm at all and should be lubricated by water on the internal face and sealed.If it leaks it needs adjusting or replacing.

When it comes to engine temps, yes the unit can lead you to problems, IF you know what you are looking for. And that is the big problem. I remember them sugesting the Water pump belt being measured. But they get fairly warm anyway. A Belt can lose about 30% of their drive energy and that is seen as heat. The real tell tale is belt dust. That means wear. The exhaust manifold can tell you some issues about the internal workings. But you have to be experienced to interpret what it means and then, what are you going to do about it anyway. Other signs will have been evedent first and then a Temp difference maybe able to tell an experienced mechanic a little more info. So in real world experience, I wouldn't worry too much. We can make things too complex for our own good at times. In the end, the Engine Temp gauge tells you what you really need to know and proper regular inspection of belts and hose clips and bolts etc are what you need to do and need to whether the IF reader shows something or not.

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Hey Shane,

 

Its probably worth noting that IR guns ( and I think that is what you have) are rated for accuracy to wildly varying percentages. The accuracy of a IR gun has a direct relationship to its purchase cost...ie...cheap ones tend to have broad accuracy ratings..ie...+/- 5 degrees of reading or some can be +/- 2% of full scale range.

 

Check your datasheet and take this into account.

 

Cheers..Gary

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The colour, surface texture and material that you are measuring affect the accuracy of reading you get.

The more expensive ones measure at two wavelengths to correct for the "emmisivity" difference.

I used to repair/calibrate/install IR thermometers when they were $10K a pop.

 

If you measure the same item repeatedly you are looking for changes, so the accuracy has less relevance.

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The colour, surface texture and material that you are measuring affect the accuracy of reading you get.

The more expensive ones measure at two wavelengths to correct for the "emmisivity" difference.

I used to repair/calibrate/install IR thermometers when they were $10K a pop.

 

If you measure the same item repeatedly you are looking for changes, so the accuracy has less relevance.

 

 

Well said :thumbup:

 

Know any lab-rats looking for work in a temp and pressure lab in Auckland?.

 

Gary

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The colour, surface texture and material that you are measuring affect the accuracy of reading you get.

The more expensive ones measure at two wavelengths to correct for the "emmisivity" difference.

I used to repair/calibrate/install IR thermometers when they were $10K a pop.

 

If you measure the same item repeatedly you are looking for changes, so the accuracy has less relevance.

 

I use a IR thermometer for measuring the temperature of steam traps to check if they are working properly, but I apply a small piece of matt black cotton insulation tape to each side of the trap, or in some cases a quick wire brush and a spray of matt black high temp paint just to get a constant "emmisivity" as it changes due to the reflectism [sp] of the surface, big difference between stainless steel, new carbon steel and old carbon steel pipes.

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Thanks for all the info guys (and Girls?)

 

The idea was to take a couple of points and do regular tests to check the engine.

 

The points I have chosen are...

 

Raw water intake

Engine cooling water entrance into heat exchanger.

Oil heat exchanger.

exhaust before water injection

Exhaust after water injection

Cooling water leaving the heat exchanger

a spot on the Sump.

 

This should give me a good indication of how she's running temperature wise.

 

Cheers

 

SHANE

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Don't get too technical shane. KISS aproach.

Raw water intake will always vary as it is ambient sea temp.

The rest varies depending on other varying factors.

The best thing to do is start engine, ceck water out exhaust and if all OK, warm engine up, (under load) and then watch engine temp gauge. Once it has gone as high as it will, you can measure the thermostate area with the IR reader and varify Gauge is ready correct. Then open engine right up hard and watch temp. If it climbs and alarms (if fitted) go off, then check temp at engine again and if it is very high, you may have a cooling problem. Pulll engine back to low RPM and allow to cool while running. NEVER switch engine off when overheated.

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