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Old 11-20-2019, 08:42 PM   #1
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City: Savannah, Ga.
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Vessel Name: Indigo Star
Vessel Model: 2006 Mainship 400
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Mainship 400 Yanmar 6LY2AN-STP Heat Exchanger Cleaning


I decided to tackle this endeavor myself when I was quoted close to 3K from the local Yanmar center to clean/service my sea water cooling system.

The engine was running fine, no temp issues, but I had no record of the cooling system ever being flushed or cleaned so it was important to me, not being familiar with this engine, to start from scratch and getting a grip on whats going on with all this water tubing. Engine hours 2180.

I paid a Yanmar tech for 2 hours just for him to get down there with me and do an inspection and to tell me what the cooling path was. We opened panels to take a peek at heat exchanger, oil lube cooler, transmission oil cooler and pre charge cooler.

Based on what he saw, he said my system was an 8 1/2 out of 10 condition. 10 being a new engine. So that was good news...anyway there was only about 2 or 3 tubes clogged and a few pieces of zincs laying around.

I ordered new heat exchanger and oil lube cooler gaskets, 4 gallons of Yanmar coolant and a new zinc kit..and just for kicks I soaked the exchanger & misc parts in vinegar overnight to remove the any unseen buildup. i also painted the components to fight off the corrosion..

So in the end, I paid for 2 hours of labor that was about $350, $175 for gaskets and coolant. But now I understand the system much better.

Anyway, I just thought to share this effort as to help anyone who might be considering this project.

I plan to re install everything this weekend and do a leak test...

Jeff in Savannah
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Old 11-20-2019, 11:34 PM   #2
Russell Clifton's Avatar
City: Anacortes Wa.
Country: usa
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Vessel Model: Defever 49 RPH
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Plus next time it will only cost $175.00 and you probably feel better about knowing more about your engine and your capability to fix it yourself.

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Old 11-21-2019, 06:47 AM   #3
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City: Southport, Florida
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Vessel Model: Mainship 30 Pilot II since 2015. GB-42 1986-2015. Former Unlimited Tonnage Master
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You can extend this maintenance interval by simply running Barnacle Barrier or Rydlime through the system from the seawater pump outlet to the seawater injection point at the exhaust riser every year using a submersible bilge pump, a bucket, and couple of hose fitting adapters and two lengths of vinyl hose. I keep this kit in an orange Home Depot bucket and can have the setup ready to circulate the descaling solution in about ten minutes.
Rich Gano
FROLIC (2005 MainShip 30 Pilot II)
Panama City area
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Old 11-24-2019, 12:33 PM   #4
City: Perdido Key, Fl.
Country: USA
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Aftercooler/Heat exchanger Cummins QSB 5.9

Has anyone serviced a Cummins QSB 5.9 cooling system? I plan to tackle and could use some advice. Thanks
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