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Old 12-01-2020, 04:44 PM   #1
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Sea Strainer Flow Meters

I've been reading up on all the posts and I see that having a functioning sea strainer is very important. Are there not any kind of flow meters you can install on your sea strainer inlet hoses that would alert you to any possible issues like blockages or decrease in flow? Just wondering for the future boat purchase.
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Old 12-01-2020, 04:53 PM   #2
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I will be interested to here the responses. Personally, I've often wondered if a vacuum gauge would work instead of a paddle wheel. I use them on my Racor fuel separators and would think they would accomplish the same thing (clogging filter increased vacuum) on a raw water system.

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Old 12-01-2020, 04:53 PM   #3
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I've seen people use a pressure gauge after the raw water pump to show intake restrictions or a weak impeller.
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Old 12-01-2020, 04:56 PM   #4
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I have a fuel flow meter installed on my Boston Whaler Revenge. I only use it for final trim on the motor but I'm guessing i could use one as a flow meter for water intake as well some day. Just dreaming of a big boat future.
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Old 12-01-2020, 05:48 PM   #5
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Discharge pressure switch after raw water pump

Our 2008 vintage Cummins 9kw generator has a barb tee on the discharge of the raw water pump. There is a pressure switch mounted on the tee that is wired into the control for the gen. It shuts the gen down very quickly if no pressure. Have had it work when the the intake to strainer plugged and when an impeller failed (not related to first shutdown). I would think one could set this up on a main engine to sound an alarm?
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Old 12-01-2020, 06:05 PM   #6
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$30 temp gauge or the more expensive $90 dollar version with a probe on exhaust elbow quickly alerts you to reduced flow

Set temp to 10 degrees above normal elbow temp.

Cheap version, been working fine since 2018 and alarm goes off well before an auto shutdown event
https://www.trawlerforum.com/forums/...arm-38822.html

More expensive dual probe version

https://www.trawlerforum.com/forums/...4&postcount=16
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Old 12-01-2020, 06:09 PM   #7
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Quote:
Originally Posted by floater View Post
I've been reading up on all the posts and I see that having a functioning sea strainer is very important. Are there not any kind of flow meters you can install on your sea strainer inlet hoses that would alert you to any possible issues like blockages or decrease in flow? Just wondering for the future boat purchase.

I like the aqua alarm system. Its not necessarily a 'meter', it is a 'flow switch' and if there is not flow, an alarm goes off. If you combine it with the exhaust temp alarm which goes off if the wet exhaust temperature gets too high, you are covered twice.



https://aqualarm.net/cooling-water-f...1fbe6fbc941ae8
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Old 12-01-2020, 06:28 PM   #8
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I see the exhaust temp setting for Aqualarm's sensor that is mounted to exterior of wet exhaust is 200-degrees. I seem to recall a prior thread where 165-degrees. Is 200-degrees an acceptable temp? I agree with bligh - nice setup to have both alarms in an dedicated panel setup. Looks like it isn't too pricey either.

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Old 12-01-2020, 07:33 PM   #9
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Exhaust gas sensor is my choice
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Old 12-01-2020, 08:05 PM   #10
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My Borel exhaust temp alarm is set for 176F. It has test wires at the band wrapped around the exhaust hose which can be touched together to test the alarm.
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Old 12-01-2020, 08:27 PM   #11
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Aqualarm raw water flow detector/alarm.

The benefit of these alarms is that they go off instantaneously the water stops flowing. Wouldn't be without one.

By the time an overheat alarm goes off, it may be too late for your impeller.
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Old 12-01-2020, 08:45 PM   #12
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Aqualarm raw water flow detector/alarm.

The benefit of these alarms is that they go off instantaneously the water stops flowing. Wouldn't be without one.

By the time an overheat alarm goes off, it may be too late for your impeller.
My impeller is getting changed regardless.
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Old 12-01-2020, 09:37 PM   #13
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Originally Posted by mvweebles View Post
I see the exhaust temp setting for Aqualarm's sensor that is mounted to exterior of wet exhaust is 200-degrees. I seem to recall a prior thread where 165-degrees. Is 200-degrees an acceptable temp? I agree with bligh - nice setup to have both alarms in an dedicated panel setup. Looks like it isn't too pricey either.

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The high temperature cutoff on the water injecting elbow on my generator trips at 230 F.
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Old 12-01-2020, 10:13 PM   #14
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Aqhalarm is the way to go. Don't try to reinvent the wheel!!!
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Old 12-01-2020, 10:37 PM   #15
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Originally Posted by boatpoker View Post
Aqualarm raw water flow detector/alarm.

The benefit of these alarms is that they go off instantaneously the water stops flowing. Wouldn't be without one.

By the time an overheat alarm goes off, it may be too late for your impeller.
But if the water is slowed/reduced those water flow alarms don't go off
But if the water is slowed/reduced the exhaust elbow will get hotter so the temp alarm I linked to will go off.

Impeller is saved as it still had water in the system albeit reduced flow.

Had ours go off last year, temp on engine was still at around 82c, slightly higher than normal but elbow had got over 50c setting off alarm, still had plenty of water flow just not as much as we should.
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Old 12-01-2020, 11:16 PM   #16
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I just bought an Aqua Alarm after my neighbor had to shut down an overheating engine while crossing the shipping lanes (shortly after making a prudent call to slow down and let a tanker pass vs throttling up to pass in front). When his port engine shut down he lost his electronic engine controls leaving him dead in the water.

He noticed the gauge but never heard an alarm. Smoke (coolant) filled the ER) in the moment it appear to be smoke, he called Mayday and the CG got him back to our marina.

His decision to slow down and let the tanker pass probably saved his life. The fact that he noticed the temp and took quick action saved his engine.

Cheap insurance to monitor water flow and exhaust temp (and fire, high water, oil and engine temp).
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Old 12-01-2020, 11:22 PM   #17
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But if the water is slowed/reduced those water flow alarms don't go off
Incorrect. I have used Aqualarm for three decades and tested at various flow rates. They most definitley will sound an alarm at some point of reduced flow (before it becomes critical). When the flow is reduced enough to let the gate fluctuate, they will activate. I have used them on an HT6-354 Perkins, a Volvo TAMD 60B and a Westerebeke 55A, the best $100 I've spent.
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Old 12-02-2020, 01:04 AM   #18
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Incorrect. I have used Aqualarm for three decades and tested at various flow rates. They most definitley will sound an alarm at some point of reduce flow

OK, my misunderstanding, its just that you and the manufacturer said......

You
Quote:
The benefit of these alarms is that they go off instantaneously the water stops flowing.
Manufacturer
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It activates an immediate alarm (not included) upon loss of raw water
I mistook stops and loss of raw water to mean that.
Reduced flow would have been a better way for me to understand.
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Old 12-02-2020, 06:38 AM   #19
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"I seem to recall a prior thread where 165-degrees. Is 200-degrees an acceptable temp?"

The use of 165F for a sea water discharge is so salt will not come out of solution and slowly plug the operation. 200F is fine warning for circulating coolant.

165F for sea water is good temperature to stay below in coolers and heat exchangers too.
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Old 12-02-2020, 06:55 AM   #20
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I have a new set of Aqua Alarm exhaust bands in my hands. One for engine and one for generator. Temp is 200 degrees. Also have Aqua Alarm high water switch. All connected to a panel with fire alarm bell. To be installed this winter. Had them on my previous boat. Great system, great company support, and reasonable price.
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