Where should I put the alarm of an exhaust alarm

tudorsailor

tudorsailor

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Having realised on a previous thread that with a dry exhaust, that I will not know there is no water flow into the engine from a block to the intake until the exhaust melts, I am having a vetus exhaust alarm fitted. If an forumnite has one already, could they tell me how loud the alarm is? I need to decide whether to have the alarm in the saloon near the engine room door, or have the alarm fitted into the cockpit somewhere. If the alarm is nice and loud, I will go with the easier option of fixing the alarm on the wall outside the engine room.

Thanks

TS
 
I have wired some simple temp controllers with the sensors just downstream of the injection elbows. I have these wired to the otherwise disused Heater plug warning lights.
 
The alarm on our boat is quite noisy, but when going full chat you just cannot hear it, so I replaced it with an led strobe light.
Its certainly very noticable in all light conditions.
 
Ours is in the cockpit. It was there when we bought the boat and I haven't put it to the test. I suppose the cockpit is the most obvious place.
On our previous boat the alarm was a different type, which was mounted inside. It was so loud it was impossible not to hear, even if you were fast asleep on the foredeck.
 
I have hard wired mine (home built) to the alarm already running from the engine (near the thermostat) - the actual alarm siren is on the engine control panel in the cockpit. A Normally Open (NO) alarm output has a diode isolator (cathode(diode stripe)) to the exhaust alarm output, anode to the thermostat switch assuming it is normally open also. Works on Yanmar YM series, don't know about others.
 
Tudor sailor

I am about to install a wet exhaust system in a yacht I am building and I am not going to have an alarm. I am going to bleed off some water from the heat exchanger before it enters the exhaust. I plan to do what "Tony" (author of the article) says and exit the bled off water just below the gunwale where I can see it

Here is the link to the article
http://www.sbmar.com/articles/designing_a_marine_exhaust_system/
 
I think this is a "must read"

http://siliconmarine.com/sm004a.html

I would use this in addition to the "rooster tail" I plan to have coming out the side of the yacht. I suppose that is a "belt and braces" approach.

ALSO

"By precisely monitoring the engines metal temperature instead of coolant temperature, the TM2 can detect engine overheating caused by low coolant, engine coolant leaks, radiator blockages, faulty thermostats, water pump failure and restricted air flow caused by grass and seeds blocking the radiator".

http://enginewatchdog.com/tm2.html

Cheers
 
Thanks for all the replies

I am installing the vetus system so the sensor is within the exhaust gases in line with the advice at silicone marine

Since the alarm is quiet, I will install the alarm in the cockpit rather than the saloon. IN fact the vetus can support two alarms from a single sensor so I could also later add 2nd alarm in the saloon in I wanted.

TudorSailor
 
tudorsailor said:
T


Since the alarm is quiet, I will install the alarm in the cockpit rather than the saloon. IN fact the vetus can support two alarms from a single sensor so I could also later add 2nd alarm in the saloon in I wanted.

TudorSailor
Click to expand...

That makes a lot of sense and as far as I know that is normal to place it there. If the alarm goes off the person at the helm may have to make a split second decision whether to abandon a maneuver or continue on.

Cheers
 
I bet the first thing that will go through the helmsman's mind is "what is that noise and what does it mean". If it is not me, I wonder how quickly they will cut the engine!

How long does it take to damage an engine through lack of cooling water intake?

Anyhow, it has to be better to have an alarm than not. At present, there is no way of knowing that there is no cooling water intake until the engine overheats! Much too late!

Thanks

TS
 
tudorsailor said:
How long does it take to damage an engine through lack of cooling water intake?

Anyhow, it has to be better to have an alarm than not. At present, there is no way of knowing that there is no cooling water intake until the engine overheats! Much too late!


TS
Click to expand...
Is your engine raw water (sea water) cooled ie. does it circulate seawater through the engine? If it does and seaweed blocks the raw water intake the seawater in your engine will boil very quickly (maybe 30 seconds?) and the temperature gauge needle will swing right up to the red section. (That would be a bit like bursting a radiator hose in your motor car)
.
Alternatively your motor may be a "closed" freshwater cooled system - you fill the engine just the same way as you do your motor car. In your motor car the heat of the engine is transferred from the engine to the outside air by the radiator (which is a heat exchanger- heat from the engine to the air). In a boat there is no radiator but a heat-exchanger instead which transfers the heat from the engine to the ocean water. In a heat exchanger the raw water from the ocean is circulated through the outer jacket and the hot freshwater from the engine through the inner jacket. The cold raw water cools the hot water from the engine.

Once the sea water has done the job of cooling the engine water it is injected into the exhaust to cool exhaust gases.
What you are doing is installing an alarm to check that there is raw water being circulated. This alarm should be in addition to the engine temperature gauge. Without your exhaust alarm the engine could function for a short time after your exhaust had been destroyed.

Now I hope you don't come back to me with "Oh I know all that. I have been working on marine engines for the last 15 years!!!)
 
Yet another device I've considered is a box with 8 (or even 16) inputs, half of which are active high, the other half low. On receiving an error signal, the box would light a LED and sound an alarm in a code sequence. My fuel/RPM gauge alarms if the alternator stops producing output (broken belt) and repeatedly sounds Morse "R" (for RPM) - dit-dah-dit

An alternative (for geeks) would be to sound a code number in binary, where dit is 0 and dah is 1. Perhaps prefixed by a long tone, as a start bit :)
 
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View attachment 38988Nigel

My 24 year old Pajero has 12 red warning lights - hand brake on, door open, brake malfunction (eg low brake fluid) etc etc. Maybe you should look at using one of them? You would need to use appropriate sensors but some of those would only be suitable switches for (say) the hand-brake or door open.

I will always use an automotive unit (where suitable) rather than a "marine" unit which invariably be double the price,
 
I have a Yanmar with closed freshwater cooling as you describe.

So, without the alarm a blockage of sea-water will result in the exhaust melting! Does not sound good. Surprising the alarm is not standard especially with a dry exhaust system with no visual check of sea water coming out the exhaust

So I didn't know all that you wrote. I have been working on human engines for past 20 years!

TS
 
tudorsailor said:
.

Surprising the alarm is not standard especially with a dry exhaust system with no visual check of sea water coming out the exhaust

So I didn't know all that you wrote. I have been working on human engines for past 20 years!

TS
Click to expand...

I think I know what you mean - there are boats designed with dry exhaust systems though. The design of my yacht will not allow me to exhaust through the transom so I am taking it out through the side of the yacht. One of the stated advantages of that is you can stick your head over the side of the yacht to see if water is coming out of the exhaust. If no water is coming out the exhaust it sounds "different" too.

In my earlier post I said I was going to "bleed off" 10% of the water after it leaves the heat exchanger and send the other 90% down the elbow into the exhaust. The raw water that I bleed off will be exited just below deck level , hopefully in a "rooster tail" so I can see it from the helm. A BIG advantage of bleeding off is that the anti-siphon loop has a hole in it (where I bleed off the water) so water cannot siphon down and fill the exhaust and motor. You might say that the anti-siphon valve will stop siphoning anyway but they can get stuck and they need periodic maintenance to make sure they work.

Cheers
 
I fitted one of these http://www.borelmfg.com/products_alarm.htm around 13year ago and also linked a water flow switch into it's alarm buzzer.
I installed the flow switch after the raw water pump.
They have altered the design now, my alarm has no panel just a PCB with wired sensor and siren attached to PCB.
It came in very handy last year !! after raw water pump failed to prime on several occasions after a fast sail.
Pete
 
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