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Old 08-18-2020, 02:56 PM   #1
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Exhaust temperature monitoring

Someone pointed out that the FIRST thing that happens when the cooling water flow is interrupted is that the temperature in the exhaust after water injection goes up, (fast) as ALL there is now there is exhaust gas. THEN the temperature of the engine starts going up. There is a lag before all that iron starts showing higher temperatures.

So they put a temperature sensor on the exhaust AFTER the water insertion point.

I like this idea. Now, my boat is all analog engine wise. But, I do have a new Garmin setup. So I am looking at NMEA2000 compatible sensors that would feed into the back bone and then display on the Garmin plotter. (Later on I want to add other parameters like fuel flow, EGT etc) I am assuming this works. Or, will I need a separate display?

Advantages are that there is only one wire to snake into each engine room, (the back bone) and no extra clutter at the helms. (Especially no need to snake up to the fly bridge as there is an NMEA cable already there for the depth sounder and autopilot)

Has anyone actually done this? I am still chewing on the Garmin manual but I keep falling asleep. Most importantly is there a way to set alarms?

Thanks.
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Old 08-18-2020, 03:08 PM   #2
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This is one area where I prefer the KISS methodology. I want to minimize risk of anything (network, mfd, configuration, etc.) preventing the delivery of critical information (i.e. Overheating). I opted for installing a Victron exhaust temp sensor in my exhaust hose and wiring it directly to a very loud (but quite small) alarm siren. No gauges at the helm at all.
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Old 08-18-2020, 03:11 PM   #3
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I'm guessing the engine(s) on the Hatteras are NA. It is helpful to see the EGT and
watch for an upward trend over time. It can warn of a gradual reduction in raw water
flow from a wearing pump or clogging heat exchanger. It should always be displayed,
IMHO.

I have used several different N-2000 sensors and they work as you describe.
If you already have a backbone then adding to it is fairly straightforward.
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Old 08-18-2020, 03:14 PM   #4
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Here's what I did - in addition to the Borel alarms already on the boat from the PO. A bit geeky, but I'm an (ex) engineer. They let me SEE the temps when I do engine room checks, however.

Exhaust Elbow Temperature Monitor/Alarms

There are lots of straightforward single-temperature DIY alarms available from several places, e.g., https://www.amazon.com/Ultimate-Prod.../dp/B00PKVF2O8
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Old 08-18-2020, 03:15 PM   #5
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Quote:
Originally Posted by KnotYet View Post
I have used several different N-2000 sensors and they work as you describe.
If you already have a backbone then adding to it is fairly straightforward.
How about displaying on the chart plotter? Alarms?

Quote:
I opted for installing a Victron exhaust temp sensor in my exhaust hose and wiring it directly to a very loud (but quite small) alarm siren. No gauges at the helm at all.
Hmmmm, that's a thought.....
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Old 08-18-2020, 03:25 PM   #6
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Quote:
Originally Posted by oscar View Post
How about displaying on the chart plotter? Alarms?
My system was on a dedicated LCD data screen but the chartplotter should do it too,
as long as it has an appropriate data field.
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Old 08-18-2020, 03:25 PM   #7
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I went with a Borel monitoring system. A small wire with 6 or 8 leads in it was all I had to run to the bridge. And my system monitors both exhaust hose temps, 2 high water alarms and 2 water in fuel sensors on my Racors. It only uses power when it is alarming. Simple install and so far very reliable. No affiliation.
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Old 08-18-2020, 08:01 PM   #8
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https://aqualarm.net/exhaust-engine-...ac61afbd217a4a
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Old 08-19-2020, 01:00 PM   #9
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There are a couple systems mentioned that work. Aqualarm and Borel
.
Another is offered by Seaboard marine. www.Sbmar.com
His, Tony Athens, is a simple temp. Sensitive snap switch that triggers an alarm. His sw. is installed on the exhaust riser/shower head. If water fails the metal parts heat almost instantly triggering the alarm.
Stand alone and nearly fool proof.

Look them all up and make your choice.

If you have a raw water failure you may have only seconds to react and shut the engine down. Coolant temp will NOT show untill long after damage occured.
Readouts, the same comment. A loud alarm will galvanize you, a readout won,t unless you are looking at it at that moment.
Consequences :
RWP impeller wrecked and chasing vane bits.
Burned exhaust hose and any fiberglass fittings.

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Old 08-19-2020, 10:03 PM   #10
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A loud alarm will galvanize you
Decades in aircraft simulators has numbed that down a wee bit. The idea is to have more time by seeing the rise in the exhaust temp right after water injection which will lead block temperature going up.
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Old 08-19-2020, 11:26 PM   #11
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I would modify that so it doesn't scare the daylights out of you but you also don't want the noise maker to simply disappear into the background noise.

Some playing with the alarm can adjust. Two quieter alarms , one at each station, may be better than one very loud one at a single station.

Piezioelectric alarms can be had in warblers which I have found better than single tones which too often blend with other noise.

But you do want it to be noted quickly to prevent damage as loss of the raw water will cause exhaust system and other damage very quickly.

If your boat is noisy then you may need a louder unit than one on a quiet boat.
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Old 08-19-2020, 11:31 PM   #12
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Quote:
Originally Posted by C lectric View Post
I would modify that so it doesn't scare the daylights out of you but you also don't want the noise maker to simply disappear into the background noise.

Some playing with the alarm can adjust. Two quieter alarms , one at each station, may be better than one very loud one at a single station.

Piezioelectric alarms can be had in warblers which I have found better than single tones which too often blend with other noise.

But you do want it to be noted quickly to prevent damage as loss of the raw water will cause exhaust system and other damage very quickly.

If your boat is noisy then you may need a louder unit than one on a quiet boat.
On past vessels I have used $12 dollar car horns from NAPA. (mounted in the engine space). Audible over the entire ship.
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Old 09-29-2020, 03:26 PM   #13
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I'm thinking of doing this as well but being an engineer, i don't want just a binary alarm. I want a gauge or numerical of some sort like the OP started out. One issue with the Borel or SBMAR alarm-type, you don't really know if its working and you'll never "test" it unless you have a serious cooling failure.
If you have a gauge or some numerical display, you'd get a feel over time what temp it normally runs.
Here's one example:
https://www.yachtd.com/products/exhaust_gas.html
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Old 09-30-2020, 07:30 PM   #14
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I understand the pros of being able to monitor actual temps and changes over time. However, I decided since I do regular cooling sytem maintenance and freshwater flush, that for me that was not necessary and another item to monitor. Without an audible alarm, I worried I could miss a problem before it became larger.
As a consequence, I installed 2 additional alarms, both audible with visual indicators to indicate which alarm is sounding. I installed the Borel exhaust hose alarm and an Aqualarm flow alarm. The flow alarm will catch any raw water flow issues such as impeller failure, blockage, or even forgetting to open the thru hull. By the time the exhaust alarm would notify me of a closed thru hull, the impeller would most likely be toast.
I chose the Borel exhaust alarm over the Aqualarm due to it's lower temperature for alarming. This alarm alerted me to a failure of my exhaust elbow (rusted through) and the resulting high temperature of the exhaust hose. I was able to catch the problem early and it saved my turbo and possibly my engine from ingesting raw water!!! Worth every penny! The Borel exhaust alarm has a method to test that it is functioning properly, and the flow alarm can easily be tested by momentarily closing the thru hull. There is a small panel mounted near the helm with labelled indicator lights and an audible alarm. It works well for me and gives a better warning of a pending overheat way before the "normal" built in overtemp alarms that come with most boats.
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Old 09-30-2020, 10:29 PM   #15
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Lost a fan belt and didn't notice the temp gauge until it was pegged at 250.
I asked my wife "Do you hear a funny noise?" Response, "Yes"
It was the buzzer under the dash happily buzzing away and blending very well with the twin Lehmans.

I will be adding a piezo screamer. (Will probably add a relay to drive piezo alarm at Helm & bridge and also LED's)
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Old 09-30-2020, 10:39 PM   #16
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https://www.ebay.com.au/itm/Engine-G...-/162710989269

$150 - simple - loud alarm

Have this on main engine and has saved us a few times.

This one for $30 is on the genset and it to has saved us a few times.

https://www.trawlerforum.com/forums/...arm-38822.html
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Old 10-01-2020, 05:26 AM   #17
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What do dry stack people,do?
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Old 10-01-2020, 06:01 AM   #18
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"What do dry stack people,do?"


If there is keel cooling the std engine alarm would show the overheat.
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Old 10-01-2020, 09:29 AM   #19
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We use a Murphy Switch.
It ‘s a coolant level float switch.
There is a see-through window (about 2.5” dia) where one can actually see the coolant level. It’s usually mounted on the side of the exhaust manifold. It has nothing to do w temps.

The audible alarm goes off when the coolant level is low but not so low that noticeably higher temps will occur.

We had a leak that triggered the alarm. Coolant temp was normal. Went back and re-anchored and searched until I found and fixed the leak. Was right before we headed out to go past Cape Caution. Probably or may have been dashed on the rocks there w the onshore breeze. Or perhaps our 400’ anchor rode could have held us off. But the Murphy Switch saved the day. Not very expensive either.
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Old 10-01-2020, 10:11 AM   #20
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My PO had one of these strapped to the exhaust using a SS hose clamp cut in half and connected to the legs on the sensor. It hadn't been reconnected after the engine was removed and rebuilt right before I bought. It wasn't the exact one shown. It was a 140 degree NO (also about $2).

I haven't yet chased down the wiring to see where it went. 140 degree might have been too low and given false alarms. They are also available in 160 and 180 degree, both of which would be reached in seconds if the raw water failed. I could shoot the cooled end of my exhaust with my IR thermometer and see which one is appropriate.

I'm thinking that, regardless of where the wires used to go, the aforementioned $12 car horn from NAPA is probably the best rewire. I really don't care to read a gauge and see that the temp is 168.34 degrees and may be rising. First, you have to look at the gauge every two minutes for it to be of any value. Second, if it's too hot then it's too hot and decimal points don't matter.

A car honking in my ER would get my attention fast. And $15 all in for a KISS system also appeals to me.
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