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Old 09-14-2022, 12:20 AM   #1
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Fresh water flush + descaling?

Trying to do this right and I have some free time at the end of the season here in the PNW Washington area. I've seen articles and videos on descaling and fresh water flushing. Do you do one or the other...or both?

As always, thanks.
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Old 09-14-2022, 05:28 PM   #2
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Freshwater flushing is a very good idea. It will help keep your raw water cooling side cleaner, less corrosive, and allow you to go longer between full servicing of the raw water side.

I am not a fan of "descaling" (ie. using products like Barnacle Buster) as a substitute for proper and complete "off engine" servicing of the various raw water components, while others here will disagree (which is fair).
Descaling should only be a temporary "clearing' of the small passages to allow for the completion of this season, so that full servicing can happen in the fall/winter (after noticing a temp rise).
Full servicing includes: removal from the engine, full cleaning using acid, ultrasonics, rodding,etc., replacement of O rings and/or gaskets, a full pressure test to ensure no internal leaks, and reassembly (possibly replacing hoses and/or clamps as needed). Also flushing (if needed) the coolant side and changing the coolant.

Full servicing will ensure that all impeller pieces, pieces of zinc, deposits, and sea creatures are removed. It will restore the "component" to "like new" condition (new gaskets etc.), and will ensure no leaks. You don't want salt water in your oil, coolant, transmission, air intake, etc. Using products like BB will only help clear away calcification, and not accomplish all of this!
Engine overheats can severely damage the engine. Internal leaks can cause extensive damage as well. Preventative maintenance is needed to improve your chances of avoiding costly damage and the associated "headaches". JMHO.
For more on freshwater flushing, see sbmar.com under "Tony's Tips" and look it up in the forums.
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Old 09-19-2022, 08:32 AM   #3
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Fresh water flush, a must in salt conditions Check out Tony's sight SBMAR.com all diesels owners should read this site.
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Old 09-19-2022, 10:42 AM   #4
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Originally Posted by Porchhound View Post
Trying to do this right and I have some free time at the end of the season here in the PNW Washington area. I've seen articles and videos on descaling and fresh water flushing. Do you do one or the other...or both?

As always, thanks.
What evidence do you have of any buildup of scale in your engine? Can you see into any raw water spaces easily? I am thinking of the heat exchangers, where an end cap can be removed for inspection. If you can do that, you will see whether there is anything that descaling could remove. If you see a clean HE, you know descaling will have little or no effect, other than ticking a single box.
What about a fresh water flush? Other than some who report here regularly, I know of no boaters with inboards who do a fresh water flush when in salt water. My own engines have never operated in fresh water, but whenever I have had the raw water side open for any reason, I have inspected for any buildup of salt and found none.
My first inboard was a raw water cooled Yanmar in a sailboat. I encountered that boat and its recent owner after 30 years. He had recently re-powered, and after removing the original engine, tore it down. He reported finding its interior to be as clean and free of salt buildup as if it was a new engine.
I suppose this could be more of an issue in saltier water, but you say you are in Puget Sound, so your water is likely similar to Vancouver BC, where I keep my boat.
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Old 09-19-2022, 10:43 AM   #5
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Fresh water flush, a must in salt conditions Check out Tony's sight SBMAR.com all diesels owners should read this site.
A must in salt water? I'm not so sure. We keep a close eye on our HXers and pull off to clean them carefully. We bore scope the after cooler water side to check for build up as well. Cooler PNW water helps maybe. Few I know fresh water flush. Lazy, no, just need based.

PS, just saw your post Keith
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Old 09-19-2022, 10:51 AM   #6
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Fresh water flushing is a preventative maintenance measure and should be done every time you use the boat. Flushing displaces the sea water and leaves fresh water which is much less prone to scaling.

Descaling with an acid solution presumably is a one time treatment for heavy scale formation. You use Barnacle Buster or equivalent and circulate a solution of it through your sea water cooling system. At least for the first exchanger in the series, usually the main heat exchanger you want to first pull the end cap and make sure the tubes are at least somewhat clear. Otherwise rod them out with a rifle cleaning rod or similar before descaling.

You shouldn't have to descale more than about once every five years.

And if you have a sea water aftercooler you want to remove it after descaling, disassemble it and clean the fin side with detergent and high pressure water. Reassemble with new o rings and lots of marine grease and pressure test it before re installing it.

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Old 09-19-2022, 10:57 AM   #7
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PS, just saw your post Keith
No we have never discussed this issue, we simply think alike.
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Old 09-19-2022, 11:18 AM   #8
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In almost three decades, I never freshwater flushed my twin FORD-Lehman 120s. I did run Rydlime through it once or twice. I thought of buying those garden hose attachments to the sea strainers used for flushing the engines, but I never did.

On the other hand, this Mainship came equipped with hose connections to the seawater hoses between the sea strainer and the pump. The Yanmar has aluminum in the seawater cooling system, and I am religious about flushing the generator and engine after every use.

I have run Barnacle Barrier through the Yanmar twice in the seven years since I bought the 2005 boat with quite a dark solution resulting from the first descaling and somewhat less so on the second descaling a couple years later.

I believe the scaling occurs during operation of the engine and not during periods of sitting with seawater in the coolers, that's when corrosion happens in addition to corrosion during operation.
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Old 09-19-2022, 03:08 PM   #9
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I started to fresh water flush when I had a new engine installed in my boat. I flush the engine and the generator with fresh water (almost) every time I return to the dock. At the same time I switched to using aluminum anodes for the engine.

I don’t think it is “necessary”. I have no data to support its value in my boat. However, it is pretty easy and makes me feel better.
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Old 09-30-2022, 03:53 PM   #10
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I think freshwater flush is very important - here in NZ we have a high saline level and we are running an TAMD70C Volvo. when we bought this it was obvious that the coolers had not been apart for a long time. The story and procedure to get them apart was long and convoluted requiring making special tools to press them out. Lots of blood ,swearing and a bigger hammer. However not wanting to do that on a regular basis we installed a freshwater quick connect between the strainer and the first exchanger ( refrigeration). This is in the shaft alley at the back of the engine. Once berthed and while the lines are being put on we have a premade hose that gets connected onto the dock water supply. The engine is left running at idle and then the isolating valve is opened . The fresh water is then turned on full. Two things happen - first if you look at the strainer it should have a reverse flow as the incoming supply is more than the engine wants - thus the strainer is purged ready for the next time. The engine then takes the freshwater and pushes it through the whole system. The engine is left idling while we connect the rest of the spring lines etc. After a minute or so you can then shut down the engine. Isolate all valves again and remove hose. This adds no more than 2 minutes to the shut down procedure . Now you have it full of freshwater so any maintenance you need to do - eg impellor - the water that leaks out is only fresh so no rust problems etc. So far after 10 years - every check reveals clear coolers . The state of them originally caused concern about long term life. Also for the 70 series - go looking for the Volvo Truck / bus parts - these are available from a number of sources at a way better price. So this is keeping the TAMD70c running perfectly - when the exchanger goes - we have a TAMD74P waiting in the garage. That is going to be a big swap so the 70 needs to stay there a bit longer. Keith
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Old 09-30-2022, 05:01 PM   #11
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If you live in a freezing climate you will do a flush when you run antifreeze through your raw water system at haul out. I use the hose adapter on my Groco filters and stick a short length of hose into a 5 gal bucket filled with antifreeze. Interior of coolers and heat exchangers appear new during periodic checks.
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Old 09-30-2022, 05:06 PM   #12
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Quote:
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I started to fresh water flush when I had a new engine installed in my boat. I flush the engine and the generator with fresh water (almost) every time I return to the dock. At the same time I switched to using aluminum anodes for the engine.

I don’t think it is “necessary”. I have no data to support its value in my boat. However, it is pretty easy and makes me feel better.
Warning on changing to aluminum zinks. You are living in a sat water environment. When you are using your boat and the engines are filled with salt you will have NO protection with the aluminum. Remember when you come back to the dock and do you flush, you still have salt in the system. You never get rid of all of it , you just minimize it. Think of it like your in brackish water, (you would still use zink anodes ) . I recommend going back to the zinks.
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Old 09-30-2022, 05:22 PM   #13
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Warning on changing to aluminum zinks. You are living in a sat water environment. When you are using your boat and the engines are filled with salt you will have NO protection with the aluminum. Remember when you come back to the dock and do you flush, you still have salt in the system. You never get rid of all of it , you just minimize it. Think of it like your in brackish water, (you would still use zink anodes ) . I recommend going back to the zinks.
I dont think that is even close to the prevailing recommendations.
Most list Al as the "universal" anode... good for all conditions as opposed to others that are limited use.
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Old 09-30-2022, 07:47 PM   #14
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Warning on changing to aluminum zinks. You are living in a sat water environment. When you are using your boat and the engines are filled with salt you will have NO protection with the aluminum. Remember when you come back to the dock and do you flush, you still have salt in the system. You never get rid of all of it , you just minimize it. Think of it like your in brackish water, (you would still use zink anodes ) . I recommend going back to the zinks.
Aluminum provides good protection for both salt and fresh. You may be thinking of Magnesium?
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Old 09-30-2022, 09:13 PM   #15
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Aluminum provides good protection for both salt and fresh. You may be thinking of Magnesium?
Nope. Aluminum for both fresh and saltwater. I can't remember the thread, but it's on this forum somewhere.

The thread is called "anodes in freshwater".
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Old 10-01-2022, 08:24 AM   #16
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People tend to forget you never get Al. What you get is an alloy. The alloys used for hull construction are quite different than used for anodes. Al alloy anodes are much less noble and will work in salt, brackish or fresh.
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Old 10-01-2022, 08:33 AM   #17
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Hey you learn something new every day. Please clarify then . What is better in salt water? I have always been told only zinc.
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Old 10-01-2022, 10:29 AM   #18
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The correct alloy for aluminum anodes gives slightly better anodic protection (higher galvanic potential) than zinc in salt water. It also has more capacity than zinc, that is, lasts longer per pound and longer per volume (even though less dense).

One problem I have had with the pencil anodes is as the aluminum corrodes (as designed) it can grow a bit in size. Zinc always seems to waste a bit in size. If the hole the pencil anode is in is tight, it can become very difficult to remove them. Make sure you are using a pencil zinc substantially smaller than the hole it occupies. In my Cummins QSB there are three 1/2" pencil anodes in 1/2 NPT holders. I am going to turn the 1/2" anodes to 7/16" to make them easier to replace.
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