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Old 26-08-2013, 19:36   #1
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Raw -> Fresh conversion?

I have a wee Volvo MD7A, runs a champ. Never seen an engine so willing to start and run. I'd like to keep it forever. Any good way to convert it to fresh water cooling? Seems like I could just add a heat exchanger and pump, but what size?

And another clarification.....on this engine the water circuit runs first through the transmission, then to the water pump on the engine, and then things get normal.
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Old 26-08-2013, 20:05   #2
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Re: Raw -> Fresh conversion?

Ours was converted with an add-on kit.

Martec. G oogle some. Good stuff.

The only b()er is it takes a small electric pump - for you need to circulate the fresh water somehow.

I think a mechanical, off the engine driven pump would be better.

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Old 26-08-2013, 20:12   #3
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Re: Raw -> Fresh conversion?

bowman do small heat exchangers,and oil coolers.
jabesco and jonhson make the small 12v hot water circulation pumps.
works a treat on my 15hp kubota

i think the heat exchanger is a size 12
http://www.ejbowman.co.uk/products/H...Exchangers.htm

http://www.ejbowman.co.uk/pdf/header.pdf
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Old 26-08-2013, 20:46   #4
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Re: Raw -> Fresh conversion?

here is a conversion of a 75 hp toyota i had on a 50 ft boat.
cant find any images of the kubota,but the principle is the same
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Old 27-08-2013, 06:57   #5
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Re: Raw -> Fresh conversion?

Why change a setup that has been working for something like 35+ years? Seems you are just adding complications to a simple engine that is functioning fine.
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Old 27-08-2013, 07:43   #6
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Re: Raw -> Fresh conversion?

I agree with Paul. Your engine is working just fine.

A fresh water system wont change any corrosion issues that you may be worried about and will cause you some maintenance problems. Fresh water cooled engines are designed to run at a much higher temperature than raw water cooled ones. I doubt that you will find the correct thermostat for your engine to run successfully with fresh water cooling. Also, if this engine is run at higher temperatures that Volvo designed it for, you may be causing some problems.

Stanley
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Old 27-08-2013, 15:35   #7
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Re: Raw -> Fresh conversion?

Just trying to do right by my baby. She has been good to me.

My car has 210,000 miles. I have attachment issues.
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Old 27-08-2013, 17:09   #8
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Re: Raw -> Fresh conversion?

Quote:
Originally Posted by hpeer View Post
Just trying to do right by my baby. She has been good to me.

My car has 210,000 miles. I have attachment issues.


Never give up
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Old 27-08-2013, 19:15   #9
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Re: Raw -> Fresh conversion?

My fave...
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Old 28-08-2013, 18:55   #10
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Re: Raw -> Fresh conversion?

Quote:
Originally Posted by hpeer View Post
I have a wee Volvo MD7A, runs a champ. Never seen an engine so willing to start and run. I'd like to keep it forever. Any good way to convert it to fresh water cooling? Seems like I could just add a heat exchanger and pump, but what size?

And another clarification.....on this engine the water circuit runs first through the transmission, then to the water pump on the engine, and then things get normal.

Is this a car or a boat? Is your plan to use your car engine in a boat?

If the latter, it would make sense to convert the boat's engine cooling from raw to fresh.

Heat exchangers--- I can only offer suggestions. You must know the fuel consumption/hour along with the raw water temperatures expected. Now at this point I am guessing that heat exchangers are rated in BTU/hr with certain raw water flow rates at temperatures. From that you should be able to make a sensible guess on the size needed.

For example, the flow rate under various head pressures are given for most pumps. Next, a gallon of home heating oil contains... if I remember correctly about 144,000 BTUs. If you then know the fuel consumption, you know how many BTUs need to be transferred via the heat exchanger.

Yes, I know some of the fuel's energy is converted to mechanical energy but I am trying to keep it simple.
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