Exhaust temperature alarm

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I'm thinking of fitting an alarm to warn me that my impellor has melted and the exhaust hose will consequently do the same very shortly! There seems to be various types - some seem to be clipped externally to the rubber exhaust hose and some seem to be invasive and need a hole drilled in the hose with a sensor inserted. The latter seems like more work and more risky? Does anybody have any experience and recommendations of what has worked well?

Thanks

Rob
 
I have a vetus through hose unit.. bullet proof...

You could even use a car temperature gauge and sender fitted to a short length of copper pipe.. temp warning is set around 70 degrees C.. (After the water injection bend of course).

Joe
 
I have fitted a flow switch in the raw water feed to the cooling pump which will show a problem quicker than an exhaust temperature alarm.

There was an article in PBO a while ago about fitting a flow switch
 
Hello Roger.
Interesting point. I dont think the end result would be any different though ?.. ie - the engine temps would not increase to a dangerous level fast enough on either system ?.
The flow sensor, I submit, is more expensive.
The exhaust temp sensor will rapidly heat to over 70 deg C after a few seconds of no water.

I think two of the best engine gauges not normally fitted are the exhaust temp sensor and a vacuum gauge in the fuel line between primary and secondary filters.. a god send..

Joe
 
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I have fitted a flow switch in the raw water feed to the cooling pump which will show a problem quicker than an exhaust temperature alarm.

There was an article in PBO a while ago about fitting a flow switch

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Yes, totally agree. I also made one of these and agree it's far better to know there's a flow problem before it getas far as the water pump.

IIRC the total cost for mine was about £15.00, but it was many years ago!!
 
I have had thermal switch on my exhaust outlets for many years. R/S Components do one that closes at 100deg.centigrade. araldite onto exhaust but dont make a very good job first time as you may hit a "hotspot".If it works ok then araldite better.you just need a 12v. supply and an alarm.
 
hmmm.. be careful... !!!!!

One of the 'problems' with the flow sensor is that it will NOT tell you if the contents of the water cooling system is being pumped into the bilges... until your engine labours through overheat about to sieze and the floor boards float.. the exhaust temp tells you of a loss of water output.. not a continuation of water INPUT, possibly to the WRONG place.

The after use fitting is imho by far the better.

Joe
 
I presume that to fit his type of sensor the hose has to be disconnected from the exhaust fitting to get a nut on the inside of the hose?
 
I also fitted a flow alarm at the beginning of last season. It saves my impellers. For some reason, probably a poor machined pump, the saildrive outlet sucks the water out of the cooling system when sailing. The pump will then not prime and the impeller shreds. I now listen for the flow alarm to stop shortly after starting. If it doesn't stop within 10 secs, I go below and fill the seawater filter with water and off we go. I know I should fit a new pump but it is expensive. Instead, this year I have fitted a non-return valve (£7 at RSS) and so far that seems to work. However, it is reassuring to hear the alarm stop and know water is flowing but perhaps it is best to have a temperature alarm as well to know all the pipe clips are done up properly as well!
 
I can see that with a sail drive a flow meter is useful on start-up. But I can look over the back and see if water is coming out!
 
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hmmm.. be careful... !!!!!

One of the 'problems' with the flow sensor is that it will NOT tell you if the contents of the water cooling system is being pumped into the bilges... until your engine labours through overheat about to sieze and the floor boards float.. the exhaust temp tells you of a loss of water output.. not a continuation of water INPUT, possibly to the WRONG place.

The after use fitting is imho by far the better.

Joe

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I'm afraid disagree, at least in part! I get a warning far EARLIER than your suggestion because the flow switch starts it's individual alarm screaming the MOMENT the water slows down or stops - just BEFORE it gets to the engine.

I accept that the position of the switch is relevant because of the risk of unseen hose/connection failure between it and the water pump, but in my case there is only about 100mm (4") between flow switch and pump so that risk is virtually eliminated.

So the simple answer, and by far the most sensible IMHO, is not to site the switch near the seacock end, but as near the engine water pump as possible. As well as making any unoticed failure extremely unlikely, the flow switch is then very handy for it's annual maintenance clean out. It is also wired via the ignition switch so the flow alarm sounds (alongside the usual ones) as soon as the ignition key is turned and stops the instant water starts flowing. Oddly, even though I know everything is ok, I STILL tend to look over transome sometimes to check!!

My switch has been installed for at least ten years and has more than earned it's keep. IMHO, waiting for the exhaust system to heat up enough to trigger an exhaust alarm, AFTER the engine has already got much hotter than designed, reminds me of shutting the stable door etc etc.

Everyone to their own etc, but the fact that you can get a flow switch for peanuts from someone like RS Components and assemble and install the whole set in half an hour, strikes me as an excellent idea.

Just wish it had been mine!! /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
 
Is the flow switch simply a unit which one fits in to the supply pipe with jubilee clips? So for example I could take the outlet from the raw water strainer and cut it, insert the flow meter and wire it in - is it as simple as that?
 
You always get water out of the exhaust outlet because the water cooling drains after the anti syphon into the exhaust. I comes out in bursts with the exhaust gases until it settles down. I was caught out when turning the engine on before an unknown marina. You see the first burst, assume everything is OK, concentrate on navigation, putting the sails away etc. and only then notice that the bursts have dwindled or stopped completely. By then the impeller is finished!
 
Hiya Jerry, and lol, I am afraid I must disagree.. I do however, fully agree that yuor short intake is good practice.. but, what if ????, being the devils advocate, the exhaust injection point hose fails.. ??

water is sensed as being pumped, bliges start to fill, engine overheats.. ??

Yes, its far fetched, but, I dont buy the fact that ANY damage could come with the use of an after event sensor... it is just too quick to respond compared to the durability of a diesel.. what are we talking here ?? 5 seconds ??.. less ??.. more...???

Probably 5 is right.. as its in the exhaust can or nearly, all pre failure points have been accounted for.

5 of one and 7 of the other me thinks lol /forums/images/graemlins/confused.gif
 
A flow switch alarm circuit (based on the one in PBO but with an improved circuit) is detailed on the Corribee website on this page. It has the details of the switch unit itself, where to buy it, and a couple of photos of the installation on a Yanmar 1gm10.
 
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Nice,, but not the best.. as said.. non lateral thinking lol

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Well, it's an opinion. I'd prefer to know that I have water at the pump. I can hear the water splashing out of the exhaust, and I maintain my engine so the chances of emptying my cooling water into the bilge are minimal. The chances of picking up a poly bag over the inlet are much higher. I'll go my way I think. /forums/images/graemlins/smile.gif
 
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but,,, the after fit alarm tells you more..

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Yes, I have to concede you're right about that bit. In my case it would tell me that the inlet was blocked, the impeller was already shredded and that all the bits of rubber vane were now lodged firmly in all the inaccessible waterways deep inside the engine block. And that my engine had already overheated.
Seriously, I don't totally disagree with your thinking, after reading your contributions carefully, but I've already fitted my alarm and felt duty bound to justify it. Did I just hear you humming 'Thorn in my Side'?
 
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