Convert Fresh water cooling to keel cooling Cummins 6BTA

[Caleb Johnson]

I run my boat in very silty and shallow sandy conditions and I cannot keep my raw water pump working so I would like to change to keel cooling. My current setup runs raw water through my aftercooler, gear oil cooler, heat exchanger and out the exhaust elbow.

I am wondering if I can just use my raw water pump to circulate coolant through my aftercooler, gear oil cooler, engine and then through an over sized fernstrum keel cooler? I understand it would be better to have two keel cooler circuits, one dedicated to the aftercooler, but I am unsure what pump to use for this.

I would likely use my jet drive to provide raw water to the exhaust elbow.

My other question would be what plumbing would be needed to remove the engine heat exchanger?

 

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[Caleb Johnson]

Thank you David for the reply.  So it sounds like the coolant circulation pump should have enough power to push coolant through the engine, transmission oil cooler and keel cooler?

And if that works than the aftercooler could be connected to a separate keel cooler and circulated with the raw water pump.

I wish this site had a picture of the coolant routing with arrows drawn in showing the flow. I saw a picture like this but it was for fuel flow.

The flow from the jet will work to cool the wet exhaust even at idle, in fact i have cooled the entire system with the flow from the jet, it works great until it blasts sand in the system! Don’t ask me how I know this!

[David Marchand]

Keel coolers typically circulate antifreeze

Keel coolers typically circulate antifreeze through the engine jacket water system which in a marine engine includes the exhaust manifold and the turbo charger. They use the so called fresh water (antifreeze) pump to do this.

If you tried to patch into this system and circulate antifreeze through the after cooler, then it would be about 100 degrees hotter than sea water and the engine’s pistons would melt at high rpms due to the intake air being too hot. That is why high performance systems use a separate keeled cooled loop for the after cooler.

So, I don’t think that you can avoid two keel coolers: one for the engine’s jacket water system and another for the after cooler. You can use the raw water pump for the after cooler system.

But then you have the problem of exhaust cooling. That is why most keeled cooled engines use a dry stack exhaust. Could you use the jet drive to provide water to cool the exhaust? Don’t know the pressure characteristics of a jet drive particularly at idle.

David

[Author]

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