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Old 17-09-2015, 05:29   #1
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Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

A couple of years ago, I installed Maretron Underbolt Temperature Sensors on the top thermostat flange and on the water pump">raw water pump of my Kohler heavy duty generator. That puts this data onto my N2K network. I read the data principally from my Maretron DSM-250 at the nav table, which I set to this screen whenever I am using the generator.

The reason why I did this is I have had problems with clogging of the sea water strainer with seaweed. This happens regularly, sometimes gradually and sometimes suddenly, but not regularly or consistently enough that there is any particular check interval which prevents problems, other than every day, which is not practical since I have bronze "fisherman" style strainers which you have to unbolt to check.

Besides seaweed, I wanted an early warning of a problem like a plastic bag.

Engine temperature is no help at all for this (my generator doesn't give me this information anyway), as there is enough capacity in the system to keep the engine cool even with significantly restricted water flow.

Having burned up a few impellers in the past, I knew that the sea water pump, which is cooled by sea water, heats up when the flow is restricted.


Now two years on I can report the following:

It works really well. I compare the pump temperature with sea water temperature (shown on my plotters). If the difference is 2 or 3 degrees, everything is ok. More than that, and I know exactly that flow is going down. And this is far before the situation gets to the point where engine running temperature is affected by even one degree.

This morning I removed a handful of seaweed after seeing that the pump temp was running 5 degrees above sea water temp. Not enough yet to cause a problem, but getting close.

The other good thing is that upon startup, you can see the pump temp drop, indicating flow, an excellent startup check.

The data is available all over the network and alarms can be set. Unfortunately not (T1-T2>Tx), but a high temperature threshold (6 or 7 degrees above usual highest sea temp) will warn of some serious sudden problem.


Overall this works surprisingly well and I can recommend it. Maybe even better would be direct measurement of raw water flow, but this is much more expensive. This approach is much cheaper and totally simple (10 minutes) to install in an engine room which already has N2K backbone in it, and works amazingly well.
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Old 17-09-2015, 06:42   #2
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

Our Westerbeke generator has a temperature sensor located at the thermostat housing which automatically shuts down the engine in case of an overheating situation. I discovered the feature when the genset water pump impeller exploded two months ago.

Is there a way you can wire the same feature into your genset?
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Old 17-09-2015, 07:19   #3
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

I don't think his issue is engine overheating but pump starvation and impeller wear. I can only assume his cooling system is oversized or more likely his gen isn't highly loaded?


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Old 17-09-2015, 07:34   #4
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

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Originally Posted by Kenomac View Post
Our Westerbeke generator has a temperature sensor located at the thermostat housing which automatically shuts down the engine in case of an overheating situation. I discovered the feature when the genset water pump impeller exploded two months ago.

Is there a way you can wire the same feature into your genset?
Ours is exactly the same. But the problem is not engine overheating but catching low raw water flow before it results in overheating -- and impeller damage. It's a different task.

By the time the system shuts down the generator, the impeller is toast.
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Old 17-09-2015, 08:46   #5
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

Sounds like a good idea to control what is, unfortunately, a very common problem.

But would measuring the exhaust hose temperature right after the exhaust elbow provide a similar if not better indication of raw water flow issues?
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Old 17-09-2015, 08:46   #6
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

Great idea, and sounds like much easier to install than setting up a differential pressure guage!
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Old 17-09-2015, 08:54   #7
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

When running offshore or for decent periods of time I try to regularly check the temperature of my engine with a simple laser temperature gun. It works great and gives me assurance that things are cooling well. I shoot all over the engine and usually get a reading back of about 95 degrees on the impeller casing which is a dozen or so degrees warmer than the water but almost 100 degrees cooler (as it should be) than the engine itself. Interesting that your readings represent only slight differences in impeller versus water temp. I am taking a reading on the metal casing which is obviously heated up in the engine compartment.
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Old 17-09-2015, 10:19   #8
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

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Originally Posted by scottthardin View Post
When running offshore or for decent periods of time I try to regularly check the temperature of my engine with a simple laser temperature gun. It works great and gives me assurance that things are cooling well. I shoot all over the engine and usually get a reading back of about 95 degrees on the impeller casing which is a dozen or so degrees warmer than the water but almost 100 degrees cooler (as it should be) than the engine itself. Interesting that your readings represent only slight differences in impeller versus water temp. I am taking a reading on the metal casing which is obviously heated up in the engine compartment.
My engine room has big blowers so stays pretty cool. A large flow of sea water (as it should be) cools down the pump to within a few degrees of the water temp.

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Old 17-09-2015, 11:00   #9
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

I love technology as much as anyone. And this is a cool setup.

But, is there a payback??

For a cruiser to start from scratch, it costs >$1300 to set this up. How many impellers can you buy for $1300??? (1300/20=65) This only protects an impeller from premature failure, impellers still get old and wear out regardless if you monitor their temperature. Yeah, yeah, you can spread the cost of the DMS250/TMP100 across other applications.

I guess I'm just a cheapass. I've been looking at the Actisense EMU-1 for several months, but can't justify the cost (~$400). It would be easy to install, my N2k network is already in one engine room, simply run wires across to the other engine. But, I'll continue to trust the Yanmar alarms to work if there's a problem.
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Old 17-09-2015, 11:26   #10
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

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Originally Posted by DotDun View Post
I love technology as much as anyone. And this is a cool setup.

But, is there a payback??

For a cruiser to start from scratch, it costs >$1300 to set this up. How many impellers can you buy for $1300??? (1300/20=65) This only protects an impeller from premature failure, impellers still get old and wear out regardless if you monitor their temperature. Yeah, yeah, you can spread the cost of the DMS250/TMP100 across other applications.

I guess I'm just a cheapass. I've been looking at the Actisense EMU-1 for several months, but can't justify the cost (~$400). It would be easy to install, my N2k network is already in one engine room, simply run wires across to the other engine. But, I'll continue to trust the Yanmar alarms to work if there's a problem.
Not to mention all the extra wires and components to maintain. that cost too. oops an other leaking fitting. I still have to go down and look. no matter how many doodads you have to conserve labor in one place, your just moving the labor to an other location. And the cost goes up. oops more labor, earning money.
KISS has great merit.
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Old 17-09-2015, 11:36   #11
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

Quote:
Originally Posted by DotDun View Post
I love technology as much as anyone. And this is a cool setup.

But, is there a payback??

For a cruiser to start from scratch, it costs >$1300 to set this up. How many impellers can you buy for $1300??? (1300/20=65) This only protects an impeller from premature failure, impellers still get old and wear out regardless if you monitor their temperature. Yeah, yeah, you can spread the cost of the DMS250/TMP100 across other applications.

I guess I'm just a cheapass. I've been looking at the Actisense EMU-1 for several months, but can't justify the cost (~$400). It would be easy to install, my N2k network is already in one engine room, simply run wires across to the other engine. But, I'll continue to trust the Yanmar alarms to work if there's a problem.

I don't know where you get $1300

The Maretron Underbolt Temp Sensor is $19.99 from Defender today.

I already had the temperature box for other purposes. Even if you don't have that, it only costs $252 (one of Maretron's more reasonably priced devices), and can have six different sensors hooked up to it.

I already had the DSM-250 which I use for a million things. But if you don't have the DSM-250, any modern instrument display and any modern plotter will display this data. I use my Tritons for this.



Bit of thread drift, but what concerns engine monitoring -- I have the Maretron Yanmar harness, and it works a treat. This was not so cheap (it was part of my big electronics refit three years ago) but I have never regretted going for it. How much time do you spend on passage behind the wheel? If you're like me, very little, especially when motoring. I love having all the engine data displayed at the scuttle. And at the nav table. The display is so good, that I even use it at the helm rather than looking down at the Yanmar gauges. I think it's important to keep an eye on your engine's vital signs, and this is really hard to do just with the normal gauges.
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Old 17-09-2015, 11:39   #12
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

Quote:
Originally Posted by tinkrman69 View Post
Not to mention all the extra wires and components to maintain. that cost too. oops an other leaking fitting. I still have to go down and look. no matter how many doodads you have to conserve labor in one place, your just moving the labor to an other location. And the cost goes up. oops more labor, earning money.
KISS has great merit.
I guess you're talking about a proper seawater flow meter? Yes, that's expensive and somewhat complicated.

My setup has zero fittings and one (1) wire, about one meter long. Nothing to maintain. And cost $19.99.
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Old 17-09-2015, 11:53   #13
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

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Originally Posted by Dockhead View Post
I don't know where you get $1300

The Maretron Underbolt Temp Sensor is $19.99 from Defender today.

I already had the temperature box for other purposes. Even if you don't have that, it only costs $252 (one of Maretron's more reasonably priced devices), and can have six different sensors hooked up to it.

I already had the DSM-250 which I use for a million things. But if you don't have the DSM-250, any modern instrument display and any modern plotter will display this data. I use my Tritons for this.



Bit of thread drift, but what concerns engine monitoring -- I have the Maretron Yanmar harness, and it works a treat. This was not so cheap (it was part of my big electronics refit three years ago) but I have never regretted going for it. How much time do you spend on passage behind the wheel? If you're like me, very little, especially when motoring. I love having all the engine data displayed at the scuttle. And at the nav table. The display is so good, that I even use it at the helm rather than looking down at the Yanmar gauges. I think it's important to keep an eye on your engine's vital signs, and this is really hard to do just with the normal gauges.
The $1300 is using prices from Maretron's website for the DMS250/TMP.

I trust the Yanmar alarms to tell me if there is a problem with an engine. I really don't care if the engine is running with 40 or 45lbs of oil pressure, or 180 or 185 degrees.

I've also found all the toys one adds eventually requires maintenance or replacement. I'd rather be sailing than fixing things.....and I'll save the $$ for burgers and beer!
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Old 17-09-2015, 12:26   #14
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

I installed a flow switch above the thru hull valve. If my strainer becomes blocked for any reason, I know about it before there is even an overheating issue.
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Old 17-09-2015, 13:20   #15
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Re: Raw Water Pump Temperature as a Proxy for Sea Water Cooling Flow

This might be a more economical way to go if you don't already have that Maretron thing.




Panel and sensor (3/4") should be less than $130.00
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