MD2030B Freshwater Cooling Circuit Flush

SimonP85 said:
Thanks all for the replies, very useful as always.

Can anyone explain this last bit below?
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You have two water circuits. One is freshwater coolant, which is a sealed system. The other is sea water, which is pumped in, through the heat exchanger/s and out through the exhaust.

When the engine is cold the fresh water stat is closed and the water does not circulate through the heat exchanger, it just gets pumped around the engine. When it reaches a pre-determined temperature the stat opens and the water circulates around the engine and through the heat exchanger, where the circulating sea water cools it. The stat will continually open and close to keep the engine at optimal temperature. This works exactly the same as it does in your car, except that the heat exchanger is replaced with a radiator and cooling fan.
 
PaulRainbow said:
You have two water circuits. One is freshwater coolant, which is a sealed system. The other is sea water, which is pumped in, through the heat exchanger/s and out through the exhaust.

When the engine is cold the fresh water stat is closed and the water does not circulate through the heat exchanger, it just gets pumped around the engine. When it reaches a pre-determined temperature the stat opens and the water circulates around the engine and through the heat exchanger, where the circulating sea water cools it. The stat will continually open and close to keep the engine at optimal temperature. This works exactly the same as it does in your car, except that the heat exchanger is replaced with a radiator and cooling fan.
Click to expand...

Thanks for this. I'm aware of the two circuits and heat exchanger to cool it. What I was more looking to understand was the route the water takes to the pump when the thermostat is closed.

Is there a passage at the front of engine block or similar so when the engine is cold water flows in via the thermostat and back to the face of the pump (blue flow in diagram below) and when the system is warm and the themostat opens water also flows to/from the heat exchanger (red flow below)? Thanks.

View attachment 65453
 
PaulR said:
one question though - dynamic descaler is not suitable if cooling circuits contain any aluminium elements - anyone know if 2030 b has any aliminium bits in the cooling circuits????
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Our 2010D had an aluminium spigot which the FW hose on the outlet from the manifold is connected to. I dont know if this is the same on your engine it is not shown on any parts lists!
 
I think you'll only get sludge in the FW system rather than scale.

I drain and replace the FW side every few years. I always drain and refill a couple of times with fresh water. It's very noticeable how much quicker it drains after the first flush.

I guess marine engines spend most of their time at idle and algae forms. No idea but it seems well worth doing.
 
yesterday we cleaned the heat exchanger from our 2030 - can't say specifically whether the crud that we got out came from the freshwater part of the exchanger or from the sea water tubes but at end of cleaning session had a surprising (to me) amount of brown sludge in the base of my container- also had to rod through 3 of the cooler tubes that had not cleared despite our soaking in dynamic descaler - now all done and looking good and drying out on radiator - our 2030 heat exchanger comprises bunch of small bore tubes housed in single larger tube- the larger outer tube having 2 large holes through which you can see some of the small bore tubes sides and has very small hole midway along length of this outer tube on opposite side to the two large holes - intend to put it back in place next time we are on board and then plan to flush the fresh water circuit - a lot
 
Why use fresh water at all? Why not a waterless glycol replacement, which doesn't have any corrosion or scaling issues?
 
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