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03-30-2014, 02:51 PM
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#1
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Guru
City: Rodney Bay Lagoon
Country: St. Lucia, West Indies
Vessel Name: "Dragon Lady"
Vessel Model: DeFever 41
Join Date: Feb 2008
Posts: 681
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Exhaust mixing elbow temperature
I want to fit gauges and/or alarms that will tell me if a mixing elbow is getting too hot. I am particularly concerned about the generator exhaust as it has a pretty blue silicone elbow just downstream of the seawater injection point (pic). Do you have such a monitoring system, and if so how does it perform? I seem to remember posts about using oven thermometers with remote gauges - any good?
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Mike
If all else fails, read the instructions
If it ain't broke, don't fix it
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03-30-2014, 05:47 PM
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#2
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Guru
City: League City, TX
Country: USA
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 928
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I like Borel Manufacturing's sensors and alarms. I've used this type of monitor on everything from a Donzi to my little Boomarang. Good stuff, works every time.
Wet Exhaust Temperature Alarm by Borel Manufacturing Inc.
Larry
M/V Boomarang
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03-30-2014, 05:53 PM
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#3
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Guru
City: Powell River, BC
Country: Canada
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 3,026
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That's a nice looking little exhaust system. The silicon hose elbow is there because of it's high temperature resistance.
I plan on purchasing some of the items from Borel when I get back to my boat next week. Thanks for the link Larry.
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03-30-2014, 06:15 PM
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#4
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Guru
City: League City, TX
Country: USA
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 928
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Quote:
Originally Posted by Northern Spy
That's a nice looking little exhaust system. The silicon hose elbow is there because of it's high temperature resistance.
I plan on purchasing some of the items from Borel when I get back to my boat next week. Thanks for the link Larry.
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Be sure to look at their home page. They make custom alarms to monitor other systems as well, in a compact, affordable package. They also have a navigation/anchor lighting panel that looks and works great.
Larry
M/V Boomarang
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03-30-2014, 06:43 PM
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#5
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Guru
City: Powell River, BC
Country: Canada
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 3,026
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Good feedback. I recognized the product from other boats i had been on and was impressed. I plan on bilge alarms, exhaust temp and the nav light panel as I am designing and building an overhead console.
[End hijack]
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03-31-2014, 05:34 AM
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#6
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Guru
City: sydney
Country: australia
Vessel Name: Aquabelle
Vessel Model: Ocean Alexander Flushdeck
Join Date: Jun 2012
Posts: 914
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Strongly recommend Boral from personal experience.
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03-31-2014, 06:42 AM
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#7
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Guru
Join Date: Apr 2009
Posts: 1,912
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Quote:
Originally Posted by Aquabelle
Strongly recommend Boral from personal experience.
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I have 2 that monitor my twins.
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Tim
Tampa Bay
Carver 355 ACMY Twin Cummins Diesels Sold
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03-31-2014, 09:43 AM
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#8
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Guru
City: Miami
Country: USA
Join Date: Jul 2013
Posts: 600
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Quote:
Originally Posted by Shoalwaters
I want to fit gauges and/or alarms that will tell me if a mixing elbow is getting too hot. I am particularly concerned about the generator exhaust as it has a pretty blue silicone elbow just downstream of the seawater injection point (pic). Do you have such a monitoring system, and if so how does it perform? I seem to remember posts about using oven thermometers with remote gauges - any good?
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If your willing to go the n2k route there are numerous other options.
Sent from my iPhone
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03-31-2014, 10:52 AM
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#9
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Guru
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 5,387
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On gennies and mains I use a switch with a setpoint around 180F and strap it on to mixing elbow with a hose clamp. I don't have the switch source readily at hand, but Borel should have them. I prefer these over sea water flow switches, as in my experience those have proven unreliable due to fouling.
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03-31-2014, 11:59 AM
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#10
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Guru
City: League City, TX
Country: USA
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 928
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Quote:
Originally Posted by Ski in NC
On gennies and mains I use a switch with a setpoint around 180F and strap it on to mixing elbow with a hose clamp. I don't have the switch source readily at hand, but Borel should have them. I prefer these over sea water flow switches, as in my experience those have proven unreliable due to fouling.
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My experience as well. The industrial-quality snap switches are about as reliable as you can get, with almost no parts to fail, simplicity itself. I believe the Borel units are rated at 165F - 170F or so, but I have never had any problems with false alarms.
Larry
M/V Boomarang
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03-31-2014, 04:32 PM
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#11
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Guru
City: Rodney Bay Lagoon
Country: St. Lucia, West Indies
Vessel Name: "Dragon Lady"
Vessel Model: DeFever 41
Join Date: Feb 2008
Posts: 681
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Ski: fixing the temperature sensor directly onto the mixing elbow makes sense to me - that is the bit that gets hot first. To my surprise Borel's instructions specify that the temperature sensor be fastened to the exhaust hose. IMHO exhaust hose is probably a fairly good heat insulator, so by the time the outer surface of the hose reaches alarm temperature, the mixing elbow has been dangerously hot for some time and my little blue elbow would be long gone! What do you use to sound the alarm from your 180F switches?
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Mike
If all else fails, read the instructions
If it ain't broke, don't fix it
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03-31-2014, 05:02 PM
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#12
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TF Site Team
City: JAX, FL
Country: USA
Vessel Name: Hobo
Vessel Model: Krogen 42-120
Join Date: Nov 2008
Posts: 7,982
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Quote:
Originally Posted by LarryM
My experience as well. The industrial-quality snap switches are about as reliable as you can get, with almost no parts to fail, simplicity itself...I have never had any problems with false alarms.
Larry
M/V Boomarang
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03-31-2014, 05:47 PM
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#13
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Guru
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 5,387
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Quote:
Originally Posted by Shoalwaters
Ski: fixing the temperature sensor directly onto the mixing elbow makes sense to me - that is the bit that gets hot first. To my surprise Borel's instructions specify that the temperature sensor be fastened to the exhaust hose. IMHO exhaust hose is probably a fairly good heat insulator, so by the time the outer surface of the hose reaches alarm temperature, the mixing elbow has been dangerously hot for some time and my little blue elbow would be long gone! What do you use to sound the alarm from your 180F switches?
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Not a simple question, really. Clamping on the mixer, once water flow stops the jacket becomes a void and heat transfer is poor. Attaching to the hose, heat transfer there is not very good either. I'm not sure which will pick up the heat first. Considering Borel's rep, I would defer to their instructions. They have probably tested in both places.
I used the mixer, partly because a SS clamp works well there, and also I use the mixer as the ground. Understood the limitations then, too.
I think either place works well enough.
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03-31-2014, 07:19 PM
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#14
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Guru
City: League City, TX
Country: USA
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 928
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Quote:
Originally Posted by Ski in NC
Not a simple question, really. Clamping on the mixer, once water flow stops the jacket becomes a void and heat transfer is poor. Attaching to the hose, heat transfer there is not very good either. I'm not sure which will pick up the heat first. Considering Borel's rep, I would defer to their instructions. They have probably tested in both places.
I used the mixer, partly because a SS clamp works well there, and also I use the mixer as the ground. Understood the limitations then, too.
I think either place works well enough.
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I agree. Aqualarm makes a very similar alarm kit and state on their website "The Wet Exhaust detector has an aluminum band that adjusts from 2" to 8", making easy installation on the elbow or flexible hose." They supply 200F switches in their kits.
My Kohler diesel generator came from the factory with a temperature sensor on the mixing elbow that will shut it down if it gets too hot.
I don't think the location would matter much on a generator or small diesel, but I know for a fact that on high-horsepower Mercruisers, the hoses can overheat if there is reduced raw water flowing through the riser due to blockage or a failing pump. The flow is sufficient to cool the riser, but there is not enough water volume to mix with, and cool the exhaust gas at high power settings. The temperature downstream of the injection point can be significantly higher than the elbow itself. In these installations the mixing occurs in the hose, not the riser, so the band is best placed on the hose since it is the most susceptible to heat damage and failure.
Again, for our purposes, I would feel comfortable with either location.
Larry
M/V Boomarang
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04-02-2014, 06:49 AM
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#16
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Guru
Join Date: Oct 2007
Posts: 19,823
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Some of what I am reading scares me.
At over about 140F i understand the salt comes out of solution and begins to coat the passages.
Sea water exhaust to a riser should be under the temperature where this happens, or failure is built in.
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04-02-2014, 10:17 AM
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#17
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Guru
City: League City, TX
Country: USA
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 928
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Quote:
Originally Posted by FF
Some of what I am reading scares me.
At over about 140F i understand the salt comes out of solution and begins to coat the passages.
Sea water exhaust to a riser should be under the temperature where this happens, or failure is built in.
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That agrees with everything I have ever seen or heard. Most raw-water cooled marine engines operated in salt water have thermostats in the 135-143F range. 140F seems to be the norm.
As to risers, going back decades, yet still true today, the general rule is that the water cooled risers should never be too hot touch even after running. So what's that 110-120 maybe 130 max?
My Yanmar mixer elbow temperature after a hard 6-hour run was 109F measured with an IR heat gun first, then with my hand. My Kohler generator runs about the same.
Larry
M/V Boomarang
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