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Old 08-31-2014, 12:01 AM   #81
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For the mains, this is usually accomplished in the docking and line securing process. ...
I agree. Still, my engine compartment remains significantly above the ambient temperature 24 hours after the engine is shut down. And regardless, my engine manufacturer warns not to run the engine at idle for more than five minutes (yes, about the time it takes to transit the marina to the berth and to begin securing the boat.) If you think I'm concerned about a rapid cool-down of engine, I'm not. The 4-cylinder engine has sufficient mass to retain heat for quite a while.
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Old 08-31-2014, 06:49 AM   #82
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>If you think I'm concerned about a rapid cool-down of engine<

The folks that worry about a rapid cool down are folks with hard working turbos.

When the unit is run hard , then simply shut down the lube oil can cook in the turbo causing carbon deposits.

These folks need a couple of min at idle before a shutdown , or an aftercooler system that pumps lube oil for 5 min or so.
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Old 08-31-2014, 05:24 PM   #83
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>If you think I'm concerned about a rapid cool-down of engine<

The folks that worry about a rapid cool down are folks with hard working turbos.

When the unit is run hard , then simply shut down the lube oil can cook in the turbo causing carbon deposits.

These folks need a couple of min at idle before a shutdown , or an aftercooler system that pumps lube oil for 5 min or so.

That's been my understanding too Fred. Have never heard of 5 minute cool down periods on non turbo diesels before.
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Old 08-31-2014, 06:10 PM   #84
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On impellers, I don't particularly worry about them inside of about two years. I worry more if the boat has sat for many months as taking a set can cause cracks, if they ran dry for some reason or a thru hull was inadvertently left closed and the engine started for a moment, or some other event that would be hard on them. But more than two years, while the impeller might well go much more, I've seen them fail. Sometimes because the replacement sat who knows where before getting put in. But most importantly, because when an impeller fails the job of changing it goes from just a few dollars and 20 minutes to something much much more. I have to then spend 20 minutes looking up the right part numbers for gaskets on my heat exchanger, 20 minutes on the phone ordering them, then I have to pick them up. Another 30 minutes getting the end caps off. I glue the gaskets with cat gasket cement on one side. If everything comes right apart, then hurray. If not, then its probably a good hour work to remove the gasket, get it scraped nice and flat and get a new one ready, per end cap and there is two. Since the end caps are off, I might as well get the rod and brush out and have a go at the heat exchanger tubes, + 1 hour. No charge at this point for the 2 seconds to pluck out the minor missing pieces of the impeller, so we have that going for us. At another 30-45 minutes to put everything back together, plus the 20 minutes it would have taken to just swap out the impeller as per usual.

Sooooo, being naturally time selfish, while I'm not a zealot for having impellers replaced every 12 months like clockwork, lets just say that I find letting them go for years and years to be a bit stress causing. Cracking the H/E open is best done at my convenience, not on unexpected discovery!
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Old 08-31-2014, 07:04 PM   #85
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Sooooo, being naturally time selfish, while I'm not a zealot for having impellers replaced every 12 months like clockwork, lets just say that I find letting them go for years and years to be a bit stress causing. Cracking the H/E open is best done at my convenience, not on unexpected discovery!
Scheduled maintenance is so much less costly and less stressful than waiting until something goes wrong. We replace by the manufacturer's recommendations and our maintenance schedules. If that means too often, then fine. But if that means we eliminate one adverse event then it's worth it.
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Old 08-31-2014, 07:55 PM   #86
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More than once I've taken a quote from one thread to start another. I should do it more often.
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Old 08-31-2014, 11:32 PM   #87
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I think an impeller change interval is dependent upon two things: the length of time the impeller has been in the pump and the frequency of the pump's being used. I believe more frequent use, or at least regular use, permits a longer change interval because the impeller is less likely to harden up and take a set.
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Old 08-31-2014, 11:55 PM   #88
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I think an impeller change interval is dependent upon two things: the length of time the impeller has been in the pump and the frequency of the pump's being used. I believe more frequent use, or at least regular use, permits a longer change interval because the impeller is less likely to harden up and take a set.
I think you're right but we still stick to our schedule. The one thing too that people need to be cautious of is impellers in their spare parts. Not accomplishing much if you replace a two year old impeller with a four year old one. Even if you have to discard some, make sure the one you're putting in is in good condition.
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Old 09-01-2014, 12:00 AM   #89
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I think you're right but we still stick to our schedule.
I've never had an experienced engine expert tell me that fresh oil is bad for an engine, and your comment reminds me that I've never had one tell me that a new impeller is bad for a pump.
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Old 09-01-2014, 06:04 AM   #90
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Another 30 minutes getting the end caps off.

Change the little screws for Allen head machine screws , the wrench can easily be inserted bt feel.
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