Is fresh water flushing worthwhile?

[David Marchand]

Years ago, following Tony’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 an 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 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?

David

 

1 user thanked author for this post.

dat715

Topic

[john plachtyna]

Fresh water Flush

Tony,

Here is the setup I installed to flush my 6LPA. Pex plumbing tubing is used to Tee into the hose before the inter cooler and runs along the inside of the hatch to the hose fitting. There is a shut off valve before the hose fitting not visible here. So far, it seems to work well.

Thanks for your advice, John

[Tony Athens]

Just more proof…….Yes it does takes some effort, but with a $100K++ in most engine rooms, seems to me it’s an extremely worthwhile endeavor.

Tony

[Rick]

800 Hours, 2009 QSC600s

Tony….thanks for your continued efforts to educate….I followed your advice
Here are the results…..First time the cores have been serviced.

[Tony Athens]

Is a Fresh Water Flush Worth while?

Took this picture today……….QSC aftercoolers that have 600 Hours on them over 6 yrs.. The owner could not understand why as he has changed zincs at least 2 time per year since new..

To question the value of fresh water flushing, or the use of zincs in fresh water is totally absurd—————-This is not less than a $10k repair as they are now junk.

I guess it’s pretty obvious these cooler sit horizontally !

Tony

[Tony Athens]

Your system looks 100% safe as to injecting fresh water someplace after the seawater pump and not running the engine………………………..If the entire muffler and exit piping is well below the spill over point on the dry riser, you have nothing to worry about.. The hose volume is not really of no concern .. Run it 3-5 minutes and you’ll be fine and you saltwater side will last 10x as long without issues…..Even stuck your hose at WOT in a 5 gallon bucket and counted seconds?…………………..Hurry

Tony

[Philip]

What kind of muffler?

Post pictures of exhaust system from turbo all the way out the Transom step by step…..

[john plachtyna]

Tony,

Here are a few pics of my exhaust system for a Yanmar 6LPA. The water inlet in on the downside
of the dry section. I’m not sure that I have achieved 12′ above the LWL due to boat design but it is close.
After the riser, the exhaust continues straight out through a muffler. Again, my question is about placing a Tee
before the intercooler to flush the engine without running it. Would this build up enough volume to adequately
flush the engine since the raw water pump is not running? Thanks for your help. John

[Tony Athens]

It may make total sense but only if the design of the exhaust system is right ..

Without good picture of the complete installation and a sketch of the exhaust design showing all elevations in relation to the LWL, I could not answer that.. It’s all about Gravity and a marble as to it rolling down hill..

Tony

[john plachtyna]

Another question

Tony,

Would it make sense to cut in a flushing line after the raw water pump so that the engine could be flushed
without running it? Would a garden hose then produce enough volume to adequately flush the engine?
I have a Yanmar 6LPA. Thanks for your help

[Tony Athens]

Good post and good experiences………….About the only thing I’ll comment on, ” that zincs don’t do anything in fresh water”—-Basically true but you left this out the other part—-They don’t need to do anything!

Tony

[mark gaudy]

a few observations and couple of questions

Interesting thoughts here. I have not posted much and I am a total novice to salty water, but have been a life long boater. I will post my experiences in the hopes that it may help some or maybe some will post to help me. In traveling the great loop, we have obviously encountered a lot of different water and it’s all, well, different. Coming from the great lakes, specifically Lake Erie, I can tell you that zinc does very little if anything on a fiberglass boat with stainless, nibral and bronze as the primary underwater metals while in my home waters. So the comments about the zinc anodes lasting longer with a freshwater flush make perfect sense. I would also guess that one might think they are useless in saltwater that is being freshwater flushed after every use because they look so good. But I assume (there’s that word again) the marine age thing comes into play here. If my 13 year old boat that has 1300 hours on it was a saltwater boat, that stays in the water all the time except for hauls for paint, thats less than 2 months of saltwater in my aftercoolers and 12 years and 10 months of fresh water (exagerated, but I was amazed when I thought of it that way) I would expect the zinc anodes to last a good long time.
The water in southwest Florida would grow a garden on my bottom in 3 weeks. The water in the keys was better even though it was warmer. The divers in Ft. Myers said that it’s a perfect storm between salt and brackish red tide coming from Okeechobee. The waters along the Carolinas are better and getting better as far as growth is concerned as we go north. Point being that where I am determines how much befifit I am getting from flushing. Now in the Chesapeake and salinity and growth is way down but I still flush, it has to help. My flush system is a little crude and requires 2 people, but it works for us for the 8 months we are in salt. I draw water through a 1″ spa hose from a full 15 gallon carboy. When the wife starts the motor,
I turn on the dock hose and the engine room wash down hose from my on board tank and run both hoses wide open. The smx pump, at an idle will suck that carboy dry through that 1″ hose with both hoses running in under 3 minutes, sometimes under 2 minutes depending on dock water pressure.
I guess my question here to those that just hook up a dock hose would be are you getting enough water to avoid pump problems down the road? Impellers are ok with that? No overheating? I was thinking that for a longer term solution, I might plumb off the fresh water tank so that they could get more water faster.
Maybe it’s not neccessary.
As far as the zincs are concerned, because I have noted that the zinc anodes do nothing in fresh water, sometime ago I switched to the aluminum mentioned earlier in this post and have used them in the salt just for convienience. The aluminum do show signs of wear in the fresh water.
When I purchased my current boat, the 8 year old original zinc anodes were about 99%. I have to change the aluminum about every three years when just in fresh water.
To the original poster of this thread, Performance Metals will sell navalloy pencils to the public. Call them and speak to Rae, she is a delightful lady who will be happy to help you.
Thanks to SB and all those that make this board possible, I’m learning every day.

[mark gaudy]

A few observations and a couple of questions

Interesting thoughts here. I have not posted much and I am a total novice to salty water, but have been a life long boater. I will post my experiences in the hopes that it may help some or maybe some will post to help me. In traveling the great loop, we have obviously encountered a lot of different water and it’s all, well, different. Coming from the great lakes, specifically Lake Erie, I can tell you that zinc does very little if anything on a fiberglass boat with stainless, nibral and bronze as the primary underwater metals while in my home waters. So the comments about the zinc anodes lasting longer with a freshwater flush make perfect sense. I would also guess that one might think they are useless in saltwater that is being freshwater flushed after every use because they look so good. But I assume (there’s that word again) the marine age thing comes into play here. If my 13 year old boat that has 1300 hours on it was a saltwater boat, that stays in the water all the time except for hauls for paint, thats less than 2 months of saltwater in my aftercoolers and 12 years and 10 months of fresh water (exagerated, but I was amazed when I thought of it that way) I would expect the zinc anodes to last a good long time.
The water in southwest Florida would grow a garden on my bottom in 3 weeks. The water in the keys was better even though it was warmer. The divers in Ft. Myers said that it’s a perfect storm between salt and brackish red tide coming from Okeechobee. The waters along the Carolinas are better and getting better as far as growth is concerned as we go north. Point being that where I am determines how much befifit I am getting from flushing. Now in the Chesapeake and salinity and growth is way down but I still flush, it has to help. My flush system is a little crude and requires 2 people, but it works for us for the 8 months we are in salt. I draw water through a 1″ spa hose attached to my strainer lid from a full 15 gallon carboy. When the wife starts the motor, I turn on the dock hose and the engine room wash down hose from my on board tank and run both hoses wide open. The smx pump, at an idle will suck that carboy dry through that 1″ hose with both hoses running in under 3 minutes, sometimes under 2 minutes depending on dock water pressure.
I guess my question here to those that just hook up a dock hose would be are you getting enough water to avoid pump problems down the road? Impellers are ok with that? I was thinking that for a longer term solution, I might plumb off the fresh water tank so that they could get more water faster. Maybe it’s not neccessary.
As far as the zincs are concerned, because I have noted that the zinc anodes do nothing in fresh water, sometime ago I switched to the aluminum mentioned earlier in this post and have used them in the salt just for convienience. The aluminum do show signs of wear in the fresh water.
When I purchased my current boat, which was always in fresh water, the 8 year old original zinc anodes were about 99%. (keep in mind my boat sits on the hard 6 months per year normally). I have to change the aluminum about every three years when just in fresh water, so they are doing something that the zinc doesn’t.
To the original poster of this thread, Performance Metals will sell navalloy pencils to the public. Call them and speak to Rae, she is a delightful lady who will be happy to help you.
Thanks to SB and all those that make this board possible, I’m learning every day.

[john plachtyna]

Groco Adaptor

I would like to add a fresh water flush to my Yanmar 6LPA. Groco makes an adaptor that mounts to the seacock or

sea strainer that a fresh water hose will then attach too. Does anyone have any experience with this part?

[Rob Schepis]

It's About Your Slip Too

Some marinas in the northeast are far inland in estuaries.  Other marinas are out near the ocean inlets.  Big difference as to what is left sitting in your seawater loop at shutdown at the end of the day…

[Rick]

It's About the Salt

Salt is salt and corrision is what you are trying to avoid.

[William Walter]

Sea water

yes the sea water up north is different then the seawater down south.usually by about 20 degrees give or take.im sure barnacle growth is quite different in many areas of the country.that was the point of my question.Bill

[Bill Fuller]

I have attached a sketch of an easy way to install a fresh water flush. Also a picture of mine both at the see strainer, where I already had a fitting, and the gunnel.

[James Pirino]

Flush setup

Can anyone share some photos and description of their freshwater flush setup.  Any ideas or photos would be great….

[Rick]

FLUSH

CAPTAIN…Is the salt water up north any different than salt water anywhere else in the world?  It doesn’t matter if you used your boat for 1 hour in salt water.  If you read all the above postings…you DO NOT want salt water left in your raw water cooling side of the engine..period.  If you are not going to use the boat in 5 days or less, flush the engines and gen set.   

[William Walter]

Flushing

ok I have a 15 foot whaler which I always flushed after every use. Being a gas engine that was salt water cooled I thought it was prudent.now I’m wondering about my Cummings diesels .i just did everything on the salt water side I could and plan to do the same in four years.boats used in northeast and is out for six months with about 100 hours of use annually.am I foolish not to have fresh water flushing.i don’t think so in my situation but would be curious to hear from people that are from my area and have the same use.

[Author]

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