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Old 19-09-2013, 18:08   #1
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Converting From Raw Water to Fresh Water Cooling

Hi There Everyone,

I did a search prior to posting but that answers I'm after were not all there.

I have an almost new yanmar ysm8 raw water cooled diesel engine in my boat, i was wondering about converting it to fresh water cooled.

So i thought i would ask people here about "Engines that they have done themselves", and see what there results were,...problems encoutered and possible fixes etc

I belive that fresh water cooled engines will outlast the raw water ones? True or false?

I believe some issues will arise from the different engine temperatures required for each system, so i was going to run a tube outside the hull ( i have a steel boat) so that the external seawater cools my pipe, therefore my cooling water for the motor, and should bring me close to the original temp if i get the pipe lengths and flow rates right.

Loss of exhaust water from motor, obviously thats going to heat up the exhaust temp, so I'm guessing that i should change the exhaust box, any other hints or tips?

The exhaust hose is currently run in an area that wont be affected by a reasonable change in temperature.

On a side note anyone ever thought of running the fuel line around the exhaust to preheat the fuel to allow for better combustion? What results did you get?

Anything that I'm missing, or other bits of information that are pertinent?

I will have other questions no doubt, but will look at any reply's first so that i ask the right questions.

Thanks in advance,

Matthew
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Old 19-09-2013, 18:15   #2
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Re: Converting From Raw Water to Fresh Water Cooling

There are thousands of 30 years boats with salt water cooled engines, still running.
Why would anyone adds complexity to the proven system? Unless you want a hot water system on board, of course .
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Old 19-09-2013, 18:23   #3
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Re: Converting From Raw Water to Fresh Water Cooling

keep it simple--more complex--more breaks when ye dont want it to ..keep it raw water cooled-nothing wrong with that.
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Old 19-09-2013, 18:26   #4
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Re: Converting From Raw Water to Fresh Water Cooling

Quote:
Originally Posted by CrazyRu View Post
There are thousands of 30 years boats with salt water cooled engines, still running.
Why would anyone adds complexity to the proven system? Unless you want a hot water system on board, of course .
CrazyRu,...

Thank you for informing me that you are happy about the thousands of old boats with raw water cooled motors still in existence, I'm glad your happy.

Thanks you for also letting me know that your not a fan of complexity

Now can you answer at least one of my questions, if there not to complex for you ???

Matthew
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Old 19-09-2013, 18:34   #5
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Re: Converting From Raw Water to Fresh Water Cooling

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Originally Posted by zeehag View Post
keep it simple--more complex--more breaks when ye dont want it to ..keep it raw water cooled-nothing wrong with that.
Zeehag, with respect.

If you haven't done the conversion that I'm looking at then what was the point of your post?

I'm after information, so that i can make my own choices thank you.

I'm not after advocates of simplicity.

Thanks.

Matthew
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Old 19-09-2013, 18:35   #6
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Re: Converting From Raw Water to Fresh Water Cooling

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CrazyRu,...

Thank you for informing me that you are happy about the thousands of old boats with raw water cooled motors still in existence, I'm glad your happy.

Thanks you for also letting me know that your not a fan of complexity

Now can you answer at least one of my questions, if there not to complex for you ???

Matthew
I believe, I answered your question. Old salt water engines are still running. They require a bit of maintenance, like flashing every year, and changing engine zincs. However, more complex engines with two cooling circles actually require more maintenance, like flashing, changing zincs and maintaining an extra set of pump, belts and hoses and a heat exchanger, they tolerate a bit more slack in maintenance, but not much.
Besides, they take a lot more room in 28 ft boat's engine compartment.
You pick.
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Old 19-09-2013, 18:37   #7
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Re: Converting From Raw Water to Fresh Water Cooling

My first engine was a Volvo raw water cooled engine. Simple? Yes. Long lived, absolutely not. After a couple years the overheating really began to bug me, so I did a conversion on it. I was able to find a "piggyback" waterpump that circulated salt water to the external heat exchanger, while simultaneously circulating the coolant between the engine and the exchanger. I thought it a great improvement, but the damage done by the first couple years never got much better. Finally, after the head gasket gave way from the heat and warpage, and the myriad other Volvo miseries (vibration, broken engine mounts, etc.) I yanked it out and put in a Yanmar 3GM30F. From Hell to Heaven for only money. When the engine was out I could look at the galleries that had carried saltwater. A nightmare. Bottom line: Life is short. Get a good, dependable engine and care for it well. It is an investment in yourself.
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Old 19-09-2013, 18:38   #8
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Re: Converting From Raw Water to Fresh Water Cooling

my 1979 yanmar is perfect and raw water cooled. never a problem it is in an ericson 35mII.
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Old 19-09-2013, 18:53   #9
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Re: Converting From Raw Water to Fresh Water Cooling

and talking about the problems you may encounter. Antifreeze have a tendency to clear cooling channels and pick up any build up engine has had. With closed circle you will need to flash it often,like every week, until it is clear. Overwise you will be facing same problems described in the post upstream, which could be easily avoided by just keeping the engine run the way it was designed.

Another note. Engines designed both as fresh and salt water cooled, require different sets of thermostats. Fresh water cooling engines have thermostats opening at higher temperature.
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Old 19-09-2013, 20:48   #10
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Re: Converting From Raw Water to Fresh Water Cooling

The thermostat should take care of regulating the engine coolant water as long as you have a large enough heat exchanger and enough raw water flow through it. Shouldn't need to change anything except adding a pump for the raw water and the heat exchanger. The currant water lift muffler should work just fine.

You are a looking at a temperature differential of less than 150 to more than 150 with a freshwater cooling system.
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Old 19-09-2013, 22:47   #11
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Re: Converting From Raw Water to Fresh Water Cooling

You talk about exhaust hoses. Hoses will not stand up to a dry exhaust system. The heat will be much more.The keel cooling system that you are talking about is a simple reliable system , but must be designed for the warmest water (I.E. stagnant harbor) that you might encounter. Also, dry exhaust is noisier than a water cooled exhaust. Good Luck with it. _____Grant.
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Old 19-09-2013, 23:10   #12
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Re: Converting From Raw Water to Fresh Water Cooling

Matt sent you a message I am going through this at the moment for a number of reasons and would be happy to chat about it

Cal
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