Raw Water Flush

Marlinmike · Feb 13, 2015

I've flushed out outboards in my early years, remember pulling exhaust plate (V6) and it was encrusted in crystallized salt like I never flushed it, I guess it could have been worse.

I have a easy setup for winterizing my diesels, I just don't do it in season as I find those that do have a tendency to stay at the dock more, I rather just fire it up and take a short ride if I want to without thinking, oh I have to flush out again when I get back. They are 16 years old and do my standard maintenance routine and all is fine.

It certainly not a bad thing, but if you use the boat a lot I think it gets subjective.

SteveH · Feb 13, 2015

RT Firefly Greetings,
Hasn't the point been mentioned, somewhere, that zinc is not a good sacrificial anode in fresh water and in fact is rendered inert by being in contact with fresh water for a period of time? So bathing your zinc in fresh water may be somewhat couterproductive in the long run yes/no? Yup, the zincs may last 3X as long but are they really doing their job if not wasting?

Exactly my question.

SteveH

DavidM · Feb 13, 2015

I believe that zincs waste slower in fresh water because fresh water is much less conductive than salt water.

David

eyschulman · Feb 13, 2015

Capt.Bill11 said:
So you're saying the salt does not return to solution as hot water passes over it the next time the engine is run?

If you want to gamble your motor on that premises Ok with me. The salts may not be what you think. There are strong acid products made to flush out cooling systems and that does not always work. To do a really good job it is often necessary to disassemble and clean a costly process.

eyschulman · Feb 13, 2015

djmarchand said:
I believe that zincs waste slower in fresh water because fresh water is much less conductive than salt water.

David

No it is because zincs in fresh water get a white coating on them that inhibits further sacrifice of their ions. The answer is to use Aluminum anodes which also work well in salt water and great for boats which switch hit.

psneeld · Feb 13, 2015

Disassembly to really do a good job.......

Thus my analysis..if all the salt doesn't go bye bye...what are you really accomplishing with flushing? Saving zincs?

Still haven't seen anything published that convinces me flushing saves engines or most engine components (except maybe a few) one bit.

Can't hurt...but is it a "PROVEN" improvement by anyone?

Something like "we run run a fleet of boats and after so many years after starting flushing, we noticed oil coolers last 30 to to percent longer as we have been using the same ones for decades and the design hasn't changed".

kchace · Feb 13, 2015

For most of our boats the only components that touch salt water are the RW pump, the heat exchangers and exhaust elbow. In my mind, the RW pump and heat exchangers are typically made of very durable (in salt water) materials. Most heat exchanger issues are related to scale build up which a fresh water rinse won't touch. Cast iron elbows start corroding the minute you take them out of the box. For those of us lucky enough to have Lehmans with SS exhaust elbows, its one less thing to worry about. (I checked mine last month and even though over 10 years old they look like new inside)

So in my mind a fresh water rinse even if it does work well would have only minimal benefits UNLESS one has a raw water cooled engine - then I think flushing is a good idea.

Ken

angus99 · Feb 13, 2015

psneeld said:
Thus my analysis..if all the salt doesn't go bye bye...what are you really accomplishing with flushing? Saving zincs?

Help me understand what you're saying, Scott. Why would all the salt need to go away for flushing to be effective? If typical seawater is 3.5% saline, does it not seem that it would be advantageous to dilute that to .0035% or whatever after a thorough freshwater flush? Which concentration is potentially more damaging to metal?

Capt.Bill11 · Feb 13, 2015

eyschulman said:
If you want to gamble your motor on that premises Ok with me. The salts may not be what you think. There are strong acid products made to flush out cooling systems and that does not always work. To do a really good job it is often necessary to disassemble and clean a costly process.

I see your point. Not sure if it's correct or not. And I'm not 100% opposed to the idea of fresh water flushing a diesel engine. Just not sure if it's all that nesscessary if you are running your engine/s on a regular basis.

I don't gamble with my engines. I give them proper and timely maintiance, thank you.

And it's rarely nesscessary to do a complete tear down to flush the raw water section of an engine. In fact I just got through flushing both my 32kw gensets, the hydraulic tank cooler, 3 - 5 ton chillers (all at once) and the NAIAD cooler by only removing the inlet and outlet hoses on the units and hooking up flush hoses.

psneeld · Feb 13, 2015

angus99 said:
Help me understand what you're saying, Scott. Why would all the salt need to go away for flushing to be effective? If typical seawater is 3.5% saline, does it not seem that it would be advantageous to dilute that to .0035% or whatever after a thorough freshwater flush? Which concentration is potentially more damaging to metal?

When the water evaporates....it is 100% salt sitting on the surface...and has been pointed out, for most of the system it really doesn't matter that much due to the materials used...but if it does, 100% salt crystal, a little moisture and air is as bad as it gets.

I'm pretty much done until someone shows definitively how it helps and I really am open to new info, but thinking something helps or feeling good about some procedure just doesn't ring my bell....

eyschulman · Feb 13, 2015

A motor run on a regular basis is less likely to have major scale and deterioration of salt water cooling systems. A motor that is used occasionally and left with salt water in it will probably be more likely to have problems not all do so its a gamble, like all smokers do not get lung cancer its a numbers game called statistics until you are it. Not all motors have the same cooling systems so some are more susceptible than others. Its not my idea to tear down parts of a cooling system for a service it is something that comes from owners manuals on certain motors. That a particular engine can limp along for 15 years with a compromised cooling SX does not mean that everybody should disregard the issue, Joe at 95 years of age always smoking 2+ packs a day did not get cancer or other lung disease does this mean the risk of cancer should be ignored. You bet I have run into a lot of hard heads during some 40 years of dealing with issues like that and rarely was there ever enough proof. For the record I say engines exposed to salt water do not do as well as those run in fresh water and anything you can do to protect the engine from salt water internal or external exposure is to the good. When cruising in salt water and using engines on a daily basis I do not flush. When letting the engines sit for some time I flush. During off season I keep the boat in fresh water and run boat around the lake for one hour every week or two. Whoever buys my boats used is a lucky or smart guy.

RT Firefly · Feb 13, 2015

Greetings,
Mr. ps. Sounds like you need one of those magnetic oil filters as well...Oh, and the magnets that align your diesel molecules for a better burn.

psneeld · Feb 13, 2015

RT Firefly said:
Greetings,
Mr. ps. Sounds like you need one of those magnetic oil filters as well...Oh, and the magnets that align your diesel molecules for a better burn.

I will do or buy almost anything that has a reasonable effect on longevity or reliability of my boat.

Just not a make work or waste money type guy.

Working in the marine trades exposes one to a lot of opinions and ideas....I try to learn the most useful and pass them along.

If freshwater flushing was such a great thing...why wouldn't at least one of the hundreds of commercial operators I know do it?

Charter guys with a hundred thousand dollars in engines don't do it...and they can't afford to miss a day fishing....you think if it were such a big deal, that only took a few minutes they wouldn't be all over it?

As I said...show me the money.

The constant bringing up of driving cars or flying airplanes or medical ideas related to boat issues can only mean that there isn't any or the poster does have anything that directly relates to the boat issue.

RT Firefly · Feb 13, 2015

I hear ya...

Capt.Bill11 · Feb 13, 2015

eyschulman said:
A motor run on a regular basis is less likely to have major scale and deterioration of salt water cooling systems. A motor that is used occasionally and left with salt water in it will probably be more likely to have problems not all do so its a gamble, like all smokers do not get lung cancer its a numbers game called statistics until you are it. Not all motors have the same cooling systems so some are more susceptible than others. Its not my idea to tear down parts of a cooling system for a service it is something that comes from owners manuals on certain motors. That a particular engine can limp along for 15 years with a compromised cooling SX does not mean that everybody should disregard the issue, Joe at 95 years of age always smoking 2+ packs a day did not get cancer or other lung disease does this mean the risk of cancer should be ignored. You bet I have run into a lot of hard heads during some 40 years of dealing with issues like that and rarely was there ever enough proof. For the record I say engines exposed to salt water do not do as well as those run in fresh water and anything you can do to protect the engine from salt water internal or external exposure is to the good. When cruising in salt water and using engines on a daily basis I do not flush. When letting the engines sit for some time I flush. During off season I keep the boat in fresh water and run boat around the lake for one hour every week or two. Whoever buys my boats used is a lucky or smart guy.

Oy vey!

eyschulman · Feb 13, 2015

The use of charter and commercial engines is different than many pleasure boats. The engines that are run thousands of hours in a year and are rebuilt or replaced in several years are in many ways different than the boat that sits at the dock idle most of the year. As for statistics and how they apply there is little difference in the concept of numbers if used in boats cars or the human machinery. Things that have variable affects manifest over a none uniform population are not always easy to quantitate, but that does not mean that the lessons learned should be disregarded. If some or many want to believe that salt water and salt air do not cause damage to their engines fine. I and others have reason to believe that the metal exterior and interior parts of an engine are better off if protected and the build up of the various salts(not all sodium chloride) and sludge that can negatively affect the raw water elements of the cooling Sx should be minimized or if possible avoided thus the flush. As I have stated before there are products made to clean out cooling systems and a good deal of this stuff is sold. If there is no problem I wonder why that is? If overheating of engines not all due to bad pumps is a common issue I wonder why? If you go to the Boatdiesiel site and research cleaning heat exchangers and look at some of the pictures of fouled exchangers maybe it will turn on a light bulb.

R_p_ryan · Oct 27, 2015

In part humor, how about one large annually replaced but cheap heat exchanger for the raw raw side, then a closed circuit fresh water loop on the original raw side. But then if have to flush the raw raw side with fresh water... Maybe I'll just go air cooled.

psneeld · Oct 27, 2015

But a fresh water flush does not guarantee no fouling...prove it.

No one else has.....or really seems to care other than those selling the products and generating a market.

I am sure done a certain way it may help...what is that way? And can it be done easily?

Then I will bite......

Deckape · Oct 27, 2015

freshwater

I agree that a boat operating daily would not benefit from flushing ,but a boat setting in a slip for a period of time might. Here in ft. Lauderdale I get a freshwater flush as I go up river ,but when getting to my slip in marathon and planing on being there for some time ,I'll flush the engines,gen with fresh water. Start each month to check systems and I'll flush thru the adapter on the strainer. Takes 30 minutes and I feel good knowing that I've tried to do what I think is the best way to add a few more years to the equipment and if it makes you feel good do it, if not ,O'well. I've seen rusted,corroded, equipment,and just shake my head and think that the owner could of done SOMETHING, rather than NOTHING at all. Just my $.02. :whistling:

R_p_ryan · Oct 28, 2015

After 30 years of direct raw water cooled outboards and outdrives in saltwater I am delighted to have an engine that is fresh water cooled with dedicated copper heat exchangers. I'd spent so many hours at launch ramps flushing the salt of engines using the dang ear muffs. Finally I said I'm spending too much time at the ramp and not enough on the water so I bought a 78 Mainship that stays in the water. I had no idea that people would flush the raw circuit since its specifically designed to protect the engine from salt water. I worked five years on a rescue boat with twin Detroits and we would run fast but baby them with maintenance like early oil changes, filter swaps, impellor changes, zincs, wire-out the exchangers. But we never rinsed the raw water circuit.

sunchaser · Oct 28, 2015

IMHO the desire to fresh water flush is dependent upon the engine, use and location. Our Perkins Sabre's have no zincs by design, HXs show no sign of scaling and we do not pull much more than 40% load routinely.
When goosed up to 80% load they do not overheat.

So, I see no reason to fresh water flush but:

if sea strainers and HXers showed signs of fouling routinely (warm water?)
or I needed to run at 70-80% load to achieve desired cruising results
or I had a salt water cooled exhaust manifold like a manifooler
had Al manifolds, or HXers

I would heartily do a fresh water flush.

So I am with RP and psneeld, not always necessary. BTW, how does a fresh water flush keep the sea strainers, and hull inlets from closing up?

R_p_ryan · Oct 28, 2015

How should I do a blowby test? Is it just at idle or when the boost pressure kicks in?

JDCAVE · Oct 28, 2015

I'm fortunate that my home port is in the Fraser River. By the time I've tied up, the main is already flushed and in the fall,/winter, it will have a low suspended silt. I also flush the genny when I get home.

Jim
Sent from my iPad using Trawler Forum

DavidM · Oct 28, 2015

R_p_ryan said:
How should I do a blowby test? Is it just at idle or when the boost pressure kicks in?

If you will PM me your email address, I will send you Cummins blowby testing procedure for 4BT, 6BT(A) and 8CT(A) engines with recommended new and worn limits. Perhaps you could adapt, extrapolate to your engine.

You usually test under load. If you have noticeable blowby at idle, you do not need to test, you are worn out.

David

R_p_ryan · Oct 29, 2015

I'm assuming the breather line,which goes to turbo inlet, should be plugged, and I should use the dipstick tube. Or I could splice in a manometer to the breather line, but I'm not convinced the pressure in the head is the same as the pressure in the case.

I'd like to do it under load and I'm hoping somebody has the pressure specifications for the T6.354

Thanks,
RR

dhays · Mar 19, 2016

Sorry to bring up an old thread, but at least I searched.

Anyone ever use something like this for doing a fresh water flush?

Secondly, I know that some connect a dock hose to the system but I have heard that this can create problems. Seems safer to use non-pressurized water and let the water pump do its job?

You all have done a great job debating the pros and cons of doing it, I don't want to reawaken that debate.

angus99 · Mar 19, 2016

dhays said:
Sorry to bring up an old thread, but at least I searched.

Anyone ever use something like this for doing a fresh water flush?

I installed these Groco flush fittings on all of my raw water intakes but have not used them yet because we're still on the hard. I'll leave it to others to tell you how foolish I am.

Steve DAntonio · Mar 19, 2016

Generally speaking I can see no reason not to fresh water flush. The conductivity of seawater and the effect the salt ion has on metal is undeniable, it's why fresh water engine rooms often look like new after 20 years. Keep this in mind, however, for heat exchangers equipped with zinc anodes, when exposed to fresh water zinc anodes, all of them, develop a coating or scale that essentially puts them to sleep, they stop working. The coating can be removed using a stiff, non-metallic brush or Scotchbtite pad. Therefore, if you flush with fresh water and it remains in the heat exchange, the zinc anodes will not work as well, or at all thereafter, unless cleaned or replaced, which could be counterproductive.

The same is true for hull anodes, vessels that operate or are stored in fresh or brackish water will face the same issue. Zinc anodes are designed for salt water use only, magnesium anodes are designed for fresh water use only,. Aluminum anodes can be used in fresh, salt or brackish water. The only caveat, aluminum anodes tend to be more active, they develop a white froth on their surface that does not impede there effectiveness, however, where pencil anodes are concerned this material can make it difficult to remove them.

dhays · Mar 19, 2016

Thanks Steve, You know more about diesel engines than I ever will.

So I will guess that your answer to;
"Anyone ever use something like this for doing a fresh water flush?" is No.

What about this question and possible hydrolock issues?
"Secondly, I know that some connect a dock hose to the system but I have heard that this can create problems. Seems safer to use non-pressurized water and let the water pump do its job?"

Larry M · Mar 19, 2016

Steve DAntonio said:
...The same is true for hull anodes, vessels that operate or are stored in fresh or brackish water will face the same issue. Zinc anodes are designed for salt water use only, magnesium anodes are designed for fresh water use only,. Aluminum anodes can be used in fresh, salt or brackish water. The only caveat, aluminum anodes tend to be more active, they develop a white froth on their surface that does not impede there effectiveness, however, where pencil anodes are concerned this material can make it difficult to remove them.

We had this issue with the pencil zincs on our FL SP135 hear exchanger also. About 3 years ago we changed everything to Al anodes on Hobo. We have been buying the pencil anodes from Performance Metals. Their pencil anodes have a steel rod core which helps keep the anode together when we're replacing/checking them. We no longer break them off as we did with the zinc.

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