The case for fresh water engine flushing

[what_barnacles]

Be aware that on certain installations incorrect flushing (pressure feeding the RW inlet) can lead to hydrolocking the engine and potentially destroying the engine.

I know of two boaters who bought the Forespar flushing valve and direct connected a garden hose to it thus hydrolocking their engines. One engine was ruined the other badly flooded.....

Yup, I can attest to that. Luckily I was able to remove the injectors and crank the water out of the cylinders. 3 oil changes later it ran again.

I didnt break a rod or a piston but I could still kick the idiot that suggested doing it on here.

 

[psneeld]

I have commercial lobstermen using the same Cummins, Cat etc. engines (though mostly no turbo's) and I have numerous engines in excess of 15 years old and 8000 - 18,000 hours that have never ever been fresh water flushed. I can't recall the last time I replaced a core pack or HX due to corrosion. For these guys the engines will rust through from the outside before they corrode from inside. I have some that are so rusty it is hard to even tell brand color but the salt water cooling circuit still works......

Never flushed, no corrosion in the raw water circuit requiring HX replacement.. IIRC this engine is a 1986 vintage..

Be aware that on certain installations incorrect flushing (pressure feeding the RW inlet) can lead to hydrolocking the engine and potentially destroying the engine.

I know of two boaters who bought the Forespar flushing valve and direct connected a garden hose to it thus hydrolocking their engines. One engine was ruined the other badly flooded.....

... If I ever heard that fresh water flushing was that great...the tens of thousands of commercial operators that frequent mags, forums, coffee shops, etc...etc...would be screaming the benefits...not a peep.

The industry has worked hard on designing materials to NOT require flushing.....

Sure it might help... a bit...maybe....possibly....

Never have seen much in the way of published proof that it does.

 

[sunchaser]

It appears you have done your homework on the subject, but I still question this and would think a descaler can take care of all of the build up inside the raw system. The fact that it runs through the entire system and wil clean the rubber hoses as well is a plus.

It is not common in my area, but apparently quite a few people on the east coast use it.

Agree, yearly is probably overkill, but how do you know it will cause corrosion? I have not used it, but from what I have read it is a fairly mild solution and no one has reported corrosion issues. We pulled apart the coolers on our 2.5 year engines and it is starting. I am therefore leaning to every few years, but still trying to figure out how to get it through the drives..long story.

FLetcher

What says your engine builder, not a marine mechanic with a Volvo hat but the builder?

 

[Lou_tribal]

I have commercial lobstermen using the same Cummins, Cat etc. engines (though mostly no turbo's) and I have numerous engines in excess of 15 years old and 8000 - 18,000 hours that have never ever been fresh water flushed. I can't recall the last time I replaced a core pack or HX due to corrosion. For these guys the engines will rust through from the outside before they corrode from inside. I have some that are so rusty it is hard to even tell brand color but the salt water cooling circuit still works......

Never flushed, no corrosion in the raw water circuit requiring HX replacement.. IIRC this engine is a 1986 vintage..

Be aware that on certain installations incorrect flushing (pressure feeding the RW inlet) can lead to hydrolocking the engine and potentially destroying the engine.

I know of two boaters who bought the Forespar flushing valve and direct connected a garden hose to it thus hydrolocking their engines. One engine was ruined the other badly flooded.....

I will need my entire life to put this number of hours on my engine

 

[dhays]

Fresh water flushing is almost entirely for corrosion mitigation, and is not expected to help with calcification. Fresh water flushing does do some good for marine critters. Marine critters were bred to thrive in a salt water environment. When a few critters are left in an engine after use but their environment is changed to fresh water, they die.

My thought is that since those marine critters are Brad to live in a salt water environment that is oxygenated, that they would die quickly in an engine cooling system without any any air exchange. Think of how raw water flush systems smell during the first flush after the system has been sitting. All the critters die as the water loses its O2.

 

[smitty477]

I have boated on the east coast in salt water for over 25 years now and have not had the need to use 'acids' tp clean the raw water systems on any engines. When winterizing we do fresh water flush before draining the system but do not fresh water flush as a rule. When disassembling any parts of the raw water systems there is little or no evidence of any 'crud' buildup within the system.
IMHO - if you insist on adding an acid to the raw water system try and keep the time limited and then follow up with a soda ash neutralization.
While it is true that these cleaning acids will not 'attack' metals such as stainless, CuNi and the like quickly they will certainly go after Al, soldered joints and brazing quite quickly.

 

[tadhana]

The corrosion problem seen with the aluminum aftercooler housings is on the air side of the system. Fresh water flushing will not flush the air side. The salt comes in with the incoming combustion air. Salt cristal built up on the walls o the after cooler. The salt laden air condenses on the tubes and on shut down will drain to the bottom. The Cummins QSB aftercoolers now have a condensate drain in the bottom air. There was a service bulletin in 2008 to correct this in earlier engines. Tony Athens has great information on this subject on his web site . http://www.sbmar.com/articles/aftercooler-thoughts-opinions-and-answers-to-some-queries/ and here is his aftercooler service guide . Cummins Marine Aftercooler Maintenance - Seaboard Marine

 

[tadhana]

I miscopied the link to the cooler service. here it is. Cummins Marine Aftercooler Maintenance - Seaboard Marine

 

[sunchaser]

The corrosion problem seen with the aluminum aftercooler housings is on the air side of the system. Fresh water flushing will not flush the air side. The salt comes in with the incoming combustion air. Salt cristal built up on the walls o the after cooler.

Would air intakes that are mounted on the outside of the hull exacerbate this situation? Especially with go fasts where spray is flying everywhere. Many slow speed vessels with inboard mounted air intakes seem to show little if any salt buildup in ER around air intakes, further noted by nil ER room corrosion.

 

[tadhana]

The placement of the air intakes will affect it somewhat. Placing the vents higher shold reduce the salt ingestion. But as you know, anytime you are running in saltwater you tend to get spray and salt on most surfaces. We run 7 KT, but have been known to have salt on top of the Bimini. I do not recall ever seeing any engine rooms with significant salt accumulations, but I do see evidence of salt crystals in the aftercoolers. It does not take much salt to create a crystal which will bridge the aluminum to bronze gap in the aftercooler. .

 

[smitty477]

"It does not take much salt to create a crystal which will bridge the aluminum to bronze gap in the aftercooler."


Yes - it is and was a poor design as shown by the attempted class action suit and the many coolers that were replace 'in warrantee' by the manufacturer.
Maintenance per Tony Athens is the best approach for these coolers.

 

[tadhana]

"It does not take much salt to create a crystal which will bridge the aluminum to bronze gap in the aftercooler."


Yes - it is and was a poor design as shown by the attempted class action suit and the many coolers that were replace 'in warrantee' by the manufacturer.
Maintenance per Tony Athens is the best approach for these coolers.

Tony also makes a good case that it was not necessarily a poor design per se. There are a lot of factors to be considered in the engineering of this component. As Tony points out, aluminum housings are common across all engine platforms. There is always room for improvement.

 

[smitty477]

"Tony also makes a good case that it was not necessarily a poor design per se. There are a lot of factors to be considered in the engineering of this component. As Tony points out, aluminum housings are common across all engine platforms. There is always room for improvement."


His position was a bit more harsh back about 12 years ago when he predicted this issue and had a fall out with Cummins - big time.
There were a number of issues he correctly predicted which helped many boating folks back then and still do - he was and is way ahead of the curve during a time when Cummins basically said there were no issues. That included the sea water pumps, intercoolers, CCV, fuel coolers, engine loading, exhaust design, vibration issues as well as belts and other problems.
IMHO he was the only person pointing out these things back in the early 90's and actually providing some real good solutions.
The fact that someone in the marine engine business who must deal daily with Cummins has softened his position a bit is not surprising nor unexpected.
I posted pics of the water side of my intercoolers earlier in this post I will try and find a picture of the air side of them since I have seen so many of them 20-35 years old (1980-1995) that have never had an issue due to the design.
There are ways to produce these types of parts so as to reduce failure and there are some subcontractors that are much better than others on the same parts.

 

[DavidM]

Agree, yearly is probably overkill, but how do you know it will cause corrosion? I have not used it, but from what I have read it is a fairly mild solution and no one has reported corrosion issues.

I did a simple red neck test to determine how corrosive Barnacle Buster is. I mixed it 50/50 as the directions indicate. Then I put a shiny common nail in the solution. It bubbled. Then I did the same with muriatic acid. I mixed it with water 30/70 like we did when I was in the chemical cleaning industry. I put the nail in the solution and it bubbled the same. The bubbling is hydrogen gas being evolved due to the acid attacking the steel. If I had left the nail in the acid overnight, I suspect it would be gone.

So, I concluded that Barnacle Buster is approximately as corrosive as muriatic acid (AKA HCL or hydrochloric acid), one of the more corrosive commercial acids (nitric acid blows right by it though -.

The matallurgy used in raw water systems- bronze and in most cases cupro-nickle is much more corrosion resistant than carbon steel. But even bronze will corrode to some extent in these acids.

So, if you need it to remove the calcium scale in your raw water system, then use it. But just proactively acid flushing every year is unnecessary and maybe harmful.

David

 

[Ski in NC]

I am just sick of Aluminum in cooling circuits. Many old engines like Detroits, Cats, Cummins use ZERO Al anywhere where it could get wet. Cummins B and C got pretty close, only thing Al was the aftercooler. Q series use even more Al. Yanmar, Volvo, anything euro AL everywhere.

Once they get a few years on them, you see where a bronze cap mates to the Al housing the bubbling is starting. Good luck getting things to seal once that process begins.

One of the first things I do when someone asks me to look at an engine is to take account of how much Al is there.

Just got off a boat with Detroit 8v71TI, 40yrs old. Looks like intercooler (basically same as an aftercooler in DD speak) is completely original, does not look like it ever has been off. No Al anywhere in cooling system.

Sendure could start making aftercoolers with no Al and would have an instant market.

 

[tadhana]

I do not believe that Sendure makes after coolers. They may make the tube bundles, but their web site does not show any after coolers.

 

[smitty477]

Here are some pics of the air side of the intercooler taken through the small easily removed inspection plate at the bottom of the cooler. This one was taken after 6 years since cleaning with about 1,000 nm per year use typically at 15-16 knots running. They typically all look like this as long as you 'bleed' the residue out of the bottom every 5 years or so. No crystals or other stuff either on the fins or sitting on the cover after removal.

 

[DavidM]

smitty:

That is an incredibly clean air side of an inter cooler. What engine is it on?

But I note that one spot on the bottom may not be representative of the entire cooler and particularly not where the air enters from the turbo. When I cleaned the air side of the after cooler on my Yanmar, it was probably that clean on the bottom. But where the air entered, it had a nice coating of oily soot. I can't imagine any air cooler on a boat not having at least some soot in that area.

Ski:

I somewhat share your concerns about aluminum. But i think that you need to make a distinction between the coolant system and the raw water system. No engine manufacturer uses aluminum in the raw water side. They (Cummins, Yanmar and others) use it on the air side and depend on an o-ring to separate the air and water which is problematic.

Yanmar, maybe alone, uses aluminum in the cooling water jacket of their exhaust manifolds. But so do many (maybe all) auto engine manufacturers use aluminum for some block and head castings. If you use the recommended antifreeze, I haven't heard of any problems with Yanmar aluminum exhaust manifolds.

David

 

[Ski in NC]

Dave- agreed that some Al components have been pretty trouble free such as Yanmar manifolds and Q Cummins coolant tanks, etc. Especially with good coolant chemistry.

Where there is trouble is where dissimilar metals make contact with each other when either in coolant or in an area where it gets damp. Inside of a mixed alloy charge air cooler, Al water pump on Fe block, Cu alloy end caps against Al coolant heat exchanger tanks, oil coolers, etc.

You are correct that no engine has Al in contact with sea water directly, but these mixed alloy junctions don't need direct contact with sea water, it is sufficient for them to get damp in a marine environment. That will set up an active cell.

 

[smitty477]

"That is an incredibly clean air side of an inter cooler. What engine is it on?"


That is a pic of Hino EH700 engine (220 Hp 6 Cyl 4 stroke TA). I have taken out and inspected/cleaned over a dozen of these on both EH700's and the newer WO6 series engines and they all look pretty clean - except for one set where someone left the air cleaners off completely.

"But I note that one spot on the bottom may not be representative of the entire cooler and particularly not where the air enters from the turbo."
This is taken with the intercooler in place by simply dropping the inspection plate so it is at the 'bottom' of the cooler and also in the middle of the cooling bundles. This is where the 'slop' tends to accumulate similarly to other designs. I do not know if I have pics of it out from the 'air side in' handy but they are just about the same - I will see of I have pics of that side as well.


"When I cleaned the air side of the after cooler on my Yanmar, it was probably that clean on the bottom."
My limited experience with Yanmar showed an oily slop but not really any soot - where did that sooty come from? My Yanmar was only really run at higher rpm and loads for what that is worth.


"But where the air entered, it had a nice coating of oily soot."
Yes - oily but not sooted up. You can see the buildup of that oily slop on the cover where I removed half of it and placed a dime next to the coated half. I see no change in boost readings on these engines between services of the intercoolers at 5-6 years at the least.
I have seen boost drops on the Cummins intercoolers when they loaded up on some of my friends install where I coaxed them into adding pyro and boost gages.
Do you run pyro and boost gages?
If yes what are their readings when you are running at or near that 270 hp rating?

 

[Fletcher500]

FLetcher What says your engine builder, not a marine mechanic with a Volvo hat but the builder?

They are in a different country, and if I was able to contact them, my guess is they would echo the predominant sentiment of the responses so far "these systems are designed to handle build up over time, they have a safety factor in the tube bundles so don't worry about it Mr. boat owner you are fine, and boil the coolers as per the manual"

In general I agree with this, because a good raw water bundle is heavy duty, and could be shot with a machine gun and still work, but there are a lot of different factors for each of us depending on the waters we boat in, are we 365 with no winterizing, etc. As noted, after 2.5 years, of running the boat almost every week, I am seeing some mild signs of build up so I want to be proactive.

I personally think the chemical cleaning is not more common because most service centers don't want to hassle with it. IE, the fluid has to circ for a few hours, so there is downtime unless the mechanic has other things to do, and then there is the disposal of the spent solution. Technically, it is harmless and it can be poured in to the ocean but a company may not want to take that chance in the event they are caught pouring it in, and someone thinks it is a haz material..but its not.

So unless its a DIY deal, and in which case you need to configure a tank, pump, find a way to pump it, etc., it wont happen. I am still unable to work on my engines myself, so I need to have certified mech's do it, while the warranty is in place.

I therefore believe weak acid solutions like RL or BB are beneficial, and I will be doing it soon, and probably very few years thereafter. You can put your hand in the stuff when its recirculating, and it warm the skin so its not a strong solution.

I am still somewhat skeptical of the fresh water flush for reasons noted. I think this has the potential to create more headaches than its worth.

 

[sunchaser]

For those who are near an ultrasonic cleaner site, it is for my money the cat's meow when cleaning after coolers. As I've heard they have been developed over the past few decades to deal with all sorts of marine cooling and heat exchanger devices on ships, USCG, ferries, large yachts and yes Lehman ACs!

 

[smitty477]

The Rydlyme that I have and use when necessary is a buffered Hydrochloric acid which will have all the same traits as that acid. Barnacle buster is stronger concentration and either will show their PH if/when they are applied to any aluminum or galvanized components on the boat or a trailer.
When I must use the circ pump with these for AC units I followed up with a mix of soda ash immediately.
The engines on my past boats had heat exchangers that were only exposed to salt water when they were running - they self drained after being turned off. So buildup could only occur during use hours. Never had any measurable buildup on the raw water sides in the many years of use with the engines.
On the coolant side where the EG also had silicates there were a number of occasions where a buildup would occur over time if the coolant was not serviced.

 

[DavidM]

I have written the first pass of the article I referred to in my original post. It covers fresh water as well as acid flushing. It is in a simple text file with all of the pics removed as the original Word file was 4 Mb and I can't upload something that big.

Let me have your comments, please.

David

 

[DavidM]

As a result of writing the article above (which I won't publish) I now believe that fresh water flushing will not do any good for most of us. Here is why:

Years ago, following Tony Athen's recommendation, I hooked up fresh water flush fittings to my engine’s strainer and started flushing religiously. Within less than a year I noticed that the engine zincs were holding up much better; in fact after three years they are still going strong. I also believed that I was reducing corrosion on my raw water metal components, particularly the after cooler. Tony has implied that you can double the interval between after cooler servicing if you flush with fresh water.
But now I have doubts about both zinc wastage and the impact on the after cooler with fresh water flushing. Here is why:


A bit of research indicates that zincs in fresh water form a protective coating that doesn’t allow any further wastage. That is one reason why my zincs have lasted for more than three years. But a question remains- does that protective coating also mean that the zinc doesn’t do any good when you go cruising for a few days in sea water? My guess is that the zinc does not do any good.


Further research indicates that for both fresh water and sea water use you should use aluminum anodes. These are available from boatzincs.com for hull anodes but not engine pencil zincs. Performance Metals is the only manufacturer that I have found for aluminum pencil zincs which they call Navalloy. Unfortunately Performance Metals doesn’t sell to the public, a review of some of their distributers comes up with only one that has aluminum anodes and these are for outboard engines, and finally Performance Metals hasn’t responded to my email asking where I can buy their pencil zincs. I can only conclude that the average boater will have a hard time buying them.


But what about the benefits to the after cooler of fresh water flushing, which was the primary reason that I started doing it. After cooler corrosion is real and results in failed after coolers and possibly failed engines if it isn’t corrected. My own limited experience indicates that corrosion starts on the aluminum housing surfaces, probably due to condensate combined with salt air corroding the aluminum. Fresh water flushing will do nothing to stop this.


I have also reviewed perhaps a dozen pics of corroded and failed after coolers and they all have extensive aluminum corrosion. Some also have minor corrosion on the bronze tube sheet which is exposed to sea water, but I suspect that it is caused by the o-ring seal failing and then galvanic action between the aluminum and bronze causes pitting on the bronze.


So, if zincs won’t work with fresh water flushing, you can’t buy aluminum anodes, and it won’t help prevent after cooler corrosion- then why do it?


Some of you on this forum have said the same thing and challenged my thinking on this question. Thanks for your input.


David

 

[smitty477]

David - I agree with your summary and do not even had zincs in my mains but I have bought many navalloy pencil zincs for outboards and for other boat owners at various places .... here is one of them "gotomarine"


Pencil Zinc replacement Aluminum Pencil Anodes, Navalloy, Secure Core,

 

[Ski in NC]

I am not sure that the zinc anode loses its effectiveness in fresh water. Just that the electrolyte loses its conductivity. Even if you flush like crazy, there will be some Na and Cl ions present to do whatever they do. I think the reaction is also mostly driven by presence or not of dissolved O2, which may be quite low in domestic fresh water sources. But then increased with aeration in the flushing process(??).

So the zincs may still be working after a flush, but simply do not waste at a high rate due to the low conductivity and lower oxygen content. The electrical potential stays the same, but the current much less.

Dave how sure are you of the anode "coating" theory? Throws up a bit of a flag to me.

I still think flushing has advantages, but minimal. I don't bother flushing my personal engine and do not make a point of recommending it to customers.

It definitely does not help in the aftercoolers which are damaged by dampness in the Al to Cu alloy junctions, a place not helped by flushing.

 

[DavidM]

Ski:

The zinc coating theory comes from Performance Metals the makers of aluminum anodes, so it may be BS. I always thought that zincs didn't waste in fresh water due to low conductivity as you said. Maybe both.

I think that your last two paragraphs says it all: minimal corrosion advantage and no after cooler benefit.

Smitty:

Thanks for the go2marine link. But I don't think I will buy any. No fresh water flush for me.

David










b

 

[ORIF]

A few engine zincs in my Cat 3208 NA's need replacing every 3-4 months or so regardless of use. I'm in full-time saltwater in Beaufort, SC and I don't flush with fresh water.

At first I thought I had a stray current. Now I'm thinking it's the battery effect for the ones that sit in a saltwater soup while connected to other metals. They're not destroyed in that amount of time, just worn enough to warrant replacement.

As mentioned in the above thread and on other sites, aluminum is supposed to last longer.

I'll switch if they really last longer and still offer the same protection.

Have any of you found the longevity claim to be definitely true?
Does 3 months sound like a problem for my zincs that are sitting and soaking in saltwater during disuse?

Thanks,

Ned

 

[tadhana]

There are two significant factors which influence the rate of corrosion between your engine zinc anodes and the other metals in the raw water system of your engine. First and foremost is the strength of the electrolyte, the raw water. Obviously salt water is a stronger electrolyte than fresh water is and corrosion of the zinc anode will be more rapid in salt water. The second is water flow. If the engine is run more hours you will see more rapid anode loss. We summer on the Chesapeake which is brackish. We get about 200 engine hours (4-6 months) out of a set of zincs. We winter in FL and we can only get about 100 engine hours (about 2-3 months) out of a set of zincs in the salt water of FL. 3-4 months in SC sounds about right to me.