Exhaust temp monitoring

[VicS]

A topic mentioned from time to time.

I just noticed a new one from Nasa Marine http://www.nasamarine.com/proddetail.php?prod=EX1 Maybe of interest

 

[nigelmercier]

A topic mentioned from time to time. I just noticed a new one from Nasa Marine

I thought this looked good, but I'm a bit worried about "Select a position on the rubber exhaust hose about 150mm back from the water injection point and drill a 5mm hole in the top ..."

 

[lw395]

I thought this looked good, but I'm a bit worried about "Select a position on the rubber exhaust hose about 150mm back from the water injection point and drill a 5mm hole in the top ..."

I assume that's back toward the blunt end of the boat, not back towards the engine?


(take care when sailing with teachers, 'forwards' often means 'towards me' rather than towards the sharp end!)

 

[VicS]

I thought this looked good, but I'm a bit worried about "Select a position on the rubber exhaust hose about 150mm back from the water injection point and drill a 5mm hole in the top ..."

I was more worried about the high temperature cable ties for fixing it to the hose than making a small hole for the sensor. I'd not heard of them before.

 

[parbuckle]

This may be useful for a quid .

 

[Salty John]

Our Sentry exhaust alarm uses a non-intrusive nylon coated stainless steel band sensor - no need to drill a hole in the exhaust hose.
http://www.saltyjohn.co.uk/sentry_cooling_water_alarm.htm

 

[pvb]

This may be useful for a quid .

With a max temp of 70C, it would be as much use as a chocolate teapot!

 

[nigelmercier]

This may be useful for a quid .

Perhaps more useful as a link or doesn't AOL eek let you do that?

 

[VicS]

This may be useful for a quid .

Difficult to tell without a proper link but I dont think you will find it has an alarm function and something would have to be improvised to fit the sensor.

 

[parbuckle]

You could stick it up the dogs backside for that kind of money.

 

[nigelmercier]

Difficult to tell without a proper link but I dont think you will find it has an alarm function and something would have to be improvised to fit the sensor.

Quite

Link in my reply above.

 

[gandy]

With a max temp of 70C, it would be as much use as a chocolate teapot!

Depends on the engine, our cooling water isn't anything like 70 deg when it comes out of the exhaust.

 

[pvb]

Depends on the engine, our cooling water isn't anything like 70 deg when it comes out of the exhaust.

I'm not sure how you can know that, have you measured the temperature at cruising revs under load? If the engine's only ticking over, the water coming out of the exhaust won't be very hot at all.

The Nasa product Vic originally mentioned measures to 170C.

 

[Trundlebug]

I bought a couple of Temperature Sensitive Switch kits from Maplins, for less than a tenner each at the time, and wired them to a buzzer as well as remote LED warning lights.

Whole kit for 2 engines was around £25, sensors were calibrated in a bowl of (just below boiling) water on the stove, and taped to the outside of the water injection point on the exhaust. No holes drilled.

Apart from the NASA kit giving real time temperature readings, it's no better than what I have - and a lot more expensive.

 

[gandy]

I'm not sure how you can know that, have you measured the temperature at cruising revs under load? If the engine's only ticking over, the water coming out of the exhaust won't be very hot at all.

The Nasa product Vic originally mentioned measures to 170C.

I don't have any way of measuring, but have checked now and again by putting my hand into the water coming out from the exhaust. 70 deg would feel very hot indeed, and as I say ours is nowhere near that even at cruising speed and fully warmed up.

Actually it would be truer to say it used not to get anything near that temp, because we do currently have an overheating problem. Nevertheless a meter reading up to 70 deg would be exactly right for our installation. I don't see how the water could ever be up to 170deg.

 

[pvb]

I don't have any way of measuring, but have checked now and again by putting my hand into the water coming out from the exhaust. 70 deg would feel very hot indeed, and as I say ours is nowhere near that even at cruising speed and fully warmed up.

Raw water cooled engines will typically have a thermostat which is fully open at 75C. Add the heat of the exhaust gas, and it's very likely that the temperature in the exhaust hose near the engine will be higher than 75C at cruising revs.

 

[VicS]

Raw water cooled engines will typically have a thermostat which is fully open at 75C. Add the heat of the exhaust gas, and it's very likely that the temperature in the exhaust hose near the engine will be higher than 75C at cruising revs.

Yes but not all the water entering the exhaust has been through the engine

Only as much as is need to cool it goes through it. The rest goes via the bypass . The two streams join before the whole lot goes to the exahaust. the combined stream will be cooler than the temp of the water leaving the engine via the thermostat.
The max will be reached if the engine is working so hard that the thermostat opens fully. Then most of the water will be reaching 75C or whatever with a small flow unheated joining via the by pass

 

[srp]

I've yet to come across an engine that produces water at the exhaust that is too hot to put your hand in, which I think means around 40 C. I know it's been through a few metres of hose and a waterlock, but that's a big drop from 75C. A good way to clean your hands when you've just gutted a load of fish, especially in winter.

 

[Ripster]

I've yet to come across an engine that produces water at the exhaust that is too hot to put your hand in, which I think means around 40 C. I know it's been through a few metres of hose and a waterlock, but that's a big drop from 75C. A good way to clean your hands when you've just gutted a load of fish, especially in winter.

Measuring along the pipe with a digital laser thermometer where the exhaust met the incoming water flow the temp was about 45 deg C. The sensors for the Exh overheat early warning alarms are 75 to 90 deg.

 

[Roberto]

Measuring along the pipe with a digital laser thermometer where the exhaust met the incoming water flow the temp was about 45 deg C. The sensors for the Exh overheat early warning alarms are 75 to 90 deg.

+1

they say 50-60°C is about the maximum one bare hand can stand, the exhaust of my indirect cooled perkins 4108 is way below that, even after one day at full-ish power

I did not even bother to measure it with my kitchen thermometre, which makes another useless expense