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Old 04-03-2020, 16:29   #1
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Boat: Lagoon 420
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Onan MDKBR on a Lagoon 420 - air in cooling water

Any idea what is going on here?

https://www.dropbox.com/s/csdw16evkl...22904.mp4?dl=0

First run after recent haulout.
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Old 04-03-2020, 21:15   #2
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Re: Onan MDKBR on a Lagoon 420 - air in cooling water

My guess the water air separator isnít working. The cooled air should exit above the port engine exhaust, the warm water should be exiting underwater just in front of the port engine. The separator is mounted above the port engine, just under the hatch /inboard. Usually I can hear the water separating
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Old 05-03-2020, 10:15   #3
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Re: Onan MDKBR on a Lagoon 420 - air in cooling water

Thanks, I guess that's a good bet but....how do these things even fail apart from splitting open?

Here's mine.
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Old 05-03-2020, 15:51   #4
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Re: Onan MDKBR on a Lagoon 420 - air in cooling water

I agree, Iím guessing since it was dry there could be an air lock? Though for this to happen; bubbles where water only should exit, Iíd think there isnít enough water flow- but the gen sensor should shut down the gen. Maybe check that this is working, Iíd look to see if I could hear and feel the water flow in the separator; then inspect the sherwood attached pump /impeller. Is there water coming out the exhaust? It could have gotten hot enough to melt and mess up the separator... certainly interesting.
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Old 05-03-2020, 16:48   #5
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Re: Onan MDKBR on a Lagoon 420 - air in cooling water

There definitely is plenty of water flow. The impeller was new less than 50 hours ago and raw water cooling is working as expected.

That said, I guess there's more moisture in the gas exhaust than usual, it seems like the gennie is "smoking" a bit, while the water exhaust is bubbling a bit. So gas included in water and water in the exhaust gas.
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Old 06-03-2020, 16:33   #6
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Re: Onan MDKBR on a Lagoon 420 - air in cooling water

Thought I'd post an update here. It was as simple as my sea cock setting for the exhaust water no longer being valid after the haul and the through-hull being cleaner than it was.

Adjusted the sea cock a smidge less open and the water separator is doing it's thing properly again.
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