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Old 02-19-2014, 03:24 PM   #21
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FWIW: Before embarking on this little project, I did a fair amount of internet reading on freshwater flushing of engines - Yanmars in particular. A significant number of the articles concluded that it is very well worth while doing so. Heat exchangers stay cleaner, corrosion markedly reduced and water injection elbows last longer. Turbos are probably happier not sleeping in a salt-laden atmosphere - at least I hope so.
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Old 02-19-2014, 03:39 PM   #22
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Heat exchangers stay cleaner, corrosion markedly reduced and water injection elbows last longer. Turbos are probably happier not sleeping in a salt-laden atmosphere - at least I hope so.
Makes sense to me. Most folks flush their outboards at the end of the season or sooner, why not the diesel inboards.
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Old 02-19-2014, 03:53 PM   #23
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If you are going to do it..there are productls like "salt away" to really enhance the process...if you have ever seen salt that has heat dried on metal...just flushing alone doesn't seem to get it all....
Salt-Away Engine Flushing ...

the system was an option on some of the early 2000's Sea Rays that I've run.
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Old 02-19-2014, 04:09 PM   #24
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I do agree with psneeld, way back in a previous life I had a 1976 V6 Merc 175 (black max), they were noted for rotting out the exhaust baffle and taking out the motor, I had a brand new power head so I faithfully flushed after every use, after 5 years figured I'd take the baffle off and take a look, I couldn't believe all the salt/mineral build up along with a corroded plate, it looked like I never flushed it.
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Old 02-19-2014, 04:15 PM   #25
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I do believe that fresh water flushing helps and so do the gurus on boatdiesel, specifically Tony Athens.

Without a doubt they will reduce zinc wastage and for no other reason that makes it worthwhile for me. Zincs cost about $10-20 per year to replace on my boat. I suspect that number will drop to a fourth of that with fresh water flushing.

Scale and marine growth will be less. A seawater kept boat will lose all of the barnacles on the bottom.(well they probably won't be gone, they will just be dead) after a few weeks in fresh water. The same thing happens to marine growth inside heat exchangers if they are left in fresh water in between sea water runs.

And even though the metals on modern heat exchangers will resist corrosion and zincs protect them even further, I like the extra benefit of freshwater sitting for 95% of the time.

It cost about $20 in parts to add a nipple, elbow and ball valve to the cover on my strainer. It takes about 5 minutes to flush after each use. Well worth it IMO.

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Old 02-19-2014, 06:29 PM   #26
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Of course flushing helps with zincs...regular zincs are not recommended for freshwater...either aluminum or magnesium alloys are...so if flushing is preserving zincs, are they really doing their job?
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Old 02-19-2014, 08:47 PM   #27
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The zincs protect the bronze castings and cupronickel tubes of the heat exchangers when they are exposed to seawater. When they are in fresh water, which should be 95% of the time in most cases if you flush with fresh water, then there will be very little corrosion of the bronze and cupronickel and little wastage of the zinc.

The fact that the zincs don't do much good in fresh water is exactly why you want to flush with fresh water. Keep the bronze/cupro-nickle in fresh water and there won't be any significant corrosion.

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Old 02-19-2014, 08:56 PM   #28
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The zincs protect the bronze castings and cupronickel tubes of the heat exchangers when they are exposed to seawater. When they are in fresh water, which should be 95% of the time in most cases if you flush with fresh water, then there will be very little corrosion of the bronze and cupronickel and little wastage of the zinc.

The fact that the zincs don't do much good in fresh water is exactly why you want to flush with fresh water. Keep the bronze/cupro-nickle in fresh water and there won't be any significant corrosion.

David
Bronze and cupro-nickle also do fine in saltwater...bronze through hulls last 50+ years in many cases.... thus why many people don't bother with fresh water flushing.

Don't get me wrong ....I'm still debating...but there's strong arguments on both sides and I just like to know the reasons that really matter.
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Old 02-22-2014, 07:09 AM   #29
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.I'm still debating...but there's strong arguments on both sides and I just like to know the reasons that really matter.

The belief that doing something ,anything is better than doing nothing.

Of course the boat is plugged into shore power 99% of the time , so with fresh water in the sea water system perhaps the zinc electrodes should be swopped for magnesium, the usual FW protection.
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