Md7a fresh water conversion heat exchanger sizeing help

[Eastward ho 24]

Cool thanks for all the input. I'll post the build as I get into it probably not till winter is here though...one last thing is your exchanger copper nickel type (cupronickel) or the straight copper? I think I'm gonna go with the copper nickel for longevity.

[gjordan]

Before a fire wiped out my shop, I had a freshwater cooled MD7A. I had to go way back in my emails to find photos from when I bought it. This was a Sendure system. The drive pulley went on the end of the camshaft where the hand crank usually goes and the pump mounted to the front of the exhaust manifold. The heat exchanger (about 12 inches high) mounted vertically on the side of the heat exchanger (near the front). It really didnt add to the overall dimensions of the engine. If you modify your engine, I would keep all of the parts needed (including the lower temp thermostat ) to change it back in case you loose a starter and need the hand crank. If you PM me your email, I will send you the photo. Grant.

[barnakiel]

Originally Posted by Eastward ho 24

Cool thanks for all the input. I'll post the build as I get into it probably not till winter is here though...one last thing is your exchanger copper nickel type (cupronickel) or the straight copper? I think I'm gonna go with the copper nickel for longevity.

How do I tell which metal it is made of?

It takes plain zinc anode. The metal, when polished, looks gold rather than red, it oxidizes in the air very fast - if you polish it now, you can't paint it tomorrow.

It does not resemble an electric wire grade copper. It is much lighter shade and feels harder too.

Martec is a Swedish company (?) I think. They probably used the better metal then for the application.

b.

[Eastward ho 24]

Copper nickel is copper with nickel alloy added. ( from what I've read I'm no expert) still looks like regular copper but it's suited for saltwater use. And copper is not. Most of the quotes I've gotten from the manufacturers were for copper I had to specifically ask for copper nickel even then some said they only made them in copper. Usually if there's the same exchanger and ones "saltwater" rated then you are safe to assume it's copper nickel. I got a few quotes that the exchanger was rated as "salt water" upon further investigation it was regular copper, so I'd say you'd need to ask the manufacturer. Other means I couldn't tell you how to tell. I could only assume the copper lines on the md7a to and from the pump are copper nickel, mine have been there since 1977. From what I understand copper is not suitable and quickly corrodes. And remember copper is ok from the coolant side but in the exchanger its exposed to the raw water on one side. I don't know how long regular copper would stand up to the test. So if my assumption is correct you could look at your md7a lines and use that as a reference but I'm sure that's not good enough but it's a start.

[Eastward ho 24]

Gjordan, thank you, however I'm using the piggy back pump so I won't need a pulley or pump, but if it's not too much to ask I could use a reference as to what the bracket looks like and its location. I'm gonna try to fabricate a bracket and I've been concerned about elevations of the exchanger. I'd like to just mount the exchanger in my lazarette and run a little extra tube so I could quick check often. I'm not sure if the extra 2 or 3 foot of tubeing would affect the pumps capacity negatively. Am I possibly over thinking this?

[barnakiel]

The tubes will run nearly horizontal thus there is very little extra pressure per ft of the tube. Some friction, but no head. Also the tubes (if rubber) are bigger diameter than the connectors on the pumps and on the exchanger, hence again little or no pressure added.

I can't tell about a piggyback pump but the electric Bosch has well in excess of any possible pressure drop - remember sweet water is in a closed circuit system - so the pressurized water goes back to the same pump but from the opposite direction. Hence, like in a power recovery pump, the pressure of the returning water helps the pump. I may be wrong but I think there is no pressure loss here.

I do not think there is any worry brewing here.

The cap of our exchanger is slightly above the engine's oil cap level. So that you can open the exchanger any time it is cold and visually check the level. You can also run the sweet water pump and visually check the flow then. The expansion tank is in the locker adjacent to the engine.

If you say copper is too vulnerable then our exchanger can only be the more noble metal - it is as a minimum 20 years old and internally pristine. Outwardly it is like new, except the very bottom part where it has the salt water connections, the anode and the back plate. A riddle, but I can live with it. Maybe one day I will discover why too.

Bueno. Have a fine day, I am off to my bunk now.

Cheers,
b.