Do Any of You Freshwater Flush Your Engine?

[Beach House]

Yes! I wish I was ambitious enough to do it every time the engine runs like you do, bravo. I’ve convinced myself it has to be beneficial.

 

[lwarden]

Well. I will see soon how well this works. After redoing all my HE and AC systems I started doing fresh water flushes religiously after every use. This is mainly for the AC which on my Cummins engines are prone to damage from salt water due to the housing design. I currently have in zinc anodes in the engines and will be checking them this weekend for wear after 5 months. Normally they needed changing every 6 months so we will see how eroded they are. Presumably if they weren't working in the mostly fresh water and have a coating on them I will see that.

I'll post the results...

 

[Comodave]

Well. I will see soon how well this works. After redoing all my HE and AC systems I started doing fresh water flushes religiously after every use. This is mainly for the AC which on my Cummins engines are prone to damage from salt water due to the housing design. I currently have in zinc anodes in the engines and will be checking them this weekend for wear after 5 months. Normally they needed changing every 6 months so we will see how eroded they are. Presumably if they weren't working in the mostly fresh water and have a coating on them I will see that.

I'll post the results...

They may have a coating or not since they are still exposed to salt water. Be interesting to see if they are eroded as much as usual or not.

 

[Senojev]

To Flush or Not to Flush

I’m wondering if there is any good evidence that fresh water flushing is beneficial. There is much anecdotal opinion on this thread but no evidence that I could see. Most of the proponents of flushing do so at the dock but what about the long term cruisers who rarely dock? Our Cummins QSB at idle will take a 5 gallon bucket of water as fast as it can be poured in the strainer. That would cut our available fresh water in half forcing us to a dock weekly. In terms of evidence, I just completed HX and AC removal for inspection and cleaning after 6 years in seawater and 1200 hrs. All were totally clean requiring just a power wash and pressure test. I do a good FW flush before winter layup and use Al anodes.

 

[Art]

Well. I will see soon how well this works. After redoing all my HE and AC systems I started doing fresh water flushes religiously after every use. This is mainly for the AC which on my Cummins engines are prone to damage from salt water due to the housing design. I currently have in zinc anodes in the engines and will be checking them this weekend for wear after 5 months. Normally they needed changing every 6 months so we will see how eroded they are. Presumably if they weren't working in the mostly fresh water and have a coating on them I will see that.

I'll post the results...

This sounds to provide the most realistic evidentiary procedure yet accounted on this thread for "what is" actually happening due to freshwater flushes; as compared to saltwater left idle after running engine.

I take that it is during this freshwater flush test [and was previously] 100% saltwater you ran in and had previously been leaving in your engines?

Lookin forward to your posted results. And, Thanks!!

 

[firehoser75]

For those looking for evidence, the best I can suggest (and have already done so twice) is to check out sbmar.com under Tony's Tips and/or the forums on that site. Tony Athens, a recognized and well respected marine diesel expert with over 35 years experience servicing marine engines, provides lots of free info and his personal experiences and opinions earned by servicing hundreds (if not thousands) of engines. His evidence is convincing. However, one would have to "go have a look" to know!

 

[Comodave]

For those looking for evidence, the best I can suggest (and have already done so twice) is to check out sbmar.com under Tony's Tips and/or the forums on that site. Tony Athens, a recognized and well respected marine diesel expert with over 35 years experience servicing marine engines, provides lots of free info and his personal experiences and opinions earned by servicing hundreds (if not thousands) of engines. His evidence is convincing. However, one would have to "go have a look" to know!

Agree 100% on Tony Athens. He is great!

 

[TF_BG]

If the fresh water is introduced into the cooling system before the water pump, technically it wouldn’t be anymore of a risk than normal raw water flowing through the same system.

This is not true with the Yanmar 4JH. Don’t ask me how I know.

 

[Hippocampus]

Very much respect Tony as very knowledgeable and full of great information. Still as prior poster suggested although he’s very experienced Tony offers his impression from that extensive experience.
Proof is you take multiple engines matched for brand and ancillaries. One group gets fresh water flushes and one group doesn’t. In all other factors they are matched (anodes and their changes, use, docking situations, salinity of waters etc.). Then compare engines and cooling systems including heat exchangers at fixed intervals. That way you can measure how much difference is made (if any) and how long to show up.
Have been told by Tony and enough others (Bob Senter comes to mind) who I respect fresh water flushes are a good idea. Also it makes sense they would be helpful. So have no disagreement with that premise. Still, the prior poster asked “is it proven?” I think it’s unproven but very strongly suggested to be true from multiple sources to the point of worth doing if feasible.

 

[Bmarler]

This is not true with the Yanmar 4JH. Don’t ask me how I know.

You damaged the yanmar by simply running fresh water through it?
Maybe explain your method and save some other yanmar owner the same fate.

 

[Comodave]

I was wondering that also? Please explain what happened.

 

[SteveA]

Fresh water flushing

Re anodes: I flush after every use with fresh water for 5 mins then run saltaway through. My Lehman SP225 has anodes in the heat exchanger and aftercooler but these coolers drain at rest so the anodes don't sit in freshwater.
So would it still be detrimental to keep my zinc anodes?
Also I've always wondered if the saltaway leaves a coating on the zincs which would affect their performance however they dissolve half away after 6 months so they must be working.

 

[lwarden]

Ok, this weekend I swapped in new zincs and have some data:

Firstly, when draining the aftercoolers I tasted the water coming out and it certainly contains salt, so I would guess I'm still pulling a lot of water from the seacock which I don't close when flushing. Probably would need to close them and re-test but don't really want to do that for obvious reasons.

The zincs I pulled were about 5 months old and from what I can tell they are only slightly less used up than normal before I flushed. The ones on the lower AC are more used up and crumbled when I hit them with pliers. I typically change them out every 6 months and they are pretty much done.

So, my assessment is: The flushing I currently do W/O closing the seacocks is probably of little use. I think I will stop doing it unless I'm going to do service on the AC or HE and/or if letting it sit for more than a couple weeks. And if I do fresh water flush I will close off the seacock in future.

One surprise was that both heat exchangers were empty of raw water and I could have sworn that when I did zinc service in the past there was raw water in there. So, not sure what is going on there but perhaps some air got in while flushing and they drained back somehow. From the piping configuration I can't see how they can drain, if someone has any clue on this or if it's common on the Cummins 370 I would appreciate it.

 

[firehoser75]

Hippo,
I agree completely with your 'analysis" of the "proven" situation. However, the reality is, to prove something using that rigorous a procedure, is very costly, and not likely to be undertaken unless there is a large profit motive involved. EG. some of the things not tested (proven) in the Covid pandemic. No profit, who would fund a very expensive study. For years we never "required" such expensive testing for everything. Experience (and repeatability) used to count for something in a lot of areas.
"Still, the prior poster asked “is it proven?” I think it’s unproven but very strongly suggested to be true from multiple sources to the point of worth doing if feasible." Agree completely with you.
I too would like to hear about the Yanmar that had issues with running FW through??
I can't picture how running FW into the sea strainer (with the engine running) instead of opening the sea cock would cause problems (but I am open to changing my mind)!

 

[Comodave]

Re anodes: I flush after every use with fresh water for 5 mins then run saltaway through. My Lehman SP225 has anodes in the heat exchanger and aftercooler but these coolers drain at rest so the anodes don't sit in freshwater.
So would it still be detrimental to keep my zinc anodes?
Also I've always wondered if the saltaway leaves a coating on the zincs which would affect their performance however they dissolve half away after 6 months so they must be working.

First thing, on your engines the aftercoolers are made of unobtanium. So what ever you can do to maintain their longevity is worth doing. Personally I would use aluminum anodes on the chance that the zincs sitting in freshwater are not doing the best job. We had these engines in our last boat. I bypassed the aftercoolers because I didn’t need that much power. The new owner wanted them hooked back up so I did it.

 

[firehoser75]

First off, I am completely unfamiliar with the Ford Lehman aftercoolers so what I am about to suggest could be moot. However, I am also reasonably sure that at least some good info can be gleamed from Tony Athens' site on aftercooler maintenance (under Tony's Tips and also on his forums) even though most of the info (but not all) is focused on Cummins.

IMHO, definitely worth taking the time checking it out, especially if your aftercooler is made of "unobtainium!!!!

 

[Comodave]

Brian at American Diesel said to take them apart every 3 or 4 years so that they wouldn’t become stuck together from corrosion, similar to what Tony Athens suggests. The good thing about the SP225 is that if you don’t need the 225HP you can very easily bypass the aftercooler and it becomes a 180HP. No adjustments or anything else needed, just pipe the water around the aftercooler and that is it. I never looked for one but Brian said they were no longer available. Might find a used one somewhere though.

The photos show how I bypassed the aftercooler. I cut the 90 degree ends off the raw water feed where it goes into and out of the aftercooler. Then connected the 2 cut ends with a hose over the top of the aftercooler seen in the last photo. The black hose with the blue stripe.

 

[backinblue]

Thanks Dave. I understand not needing the power, but what is the advantage of bypassing vs. just leaving them connected?

 

[Comodave]

It saves the aftercooler for future use by someone that wants the power. The buyer of that boat wanted them hooked up so I hooked them up, took 15 minutes.

 

[firehoser75]

To expound on Dave's answer..... As long as saltwater is passing through and left sitting in the aftercooler, you have a potential recipe for (extensive) corrosion. Basically they act like a "battery": meaning dissimilar metals in an electrolyte (saltwater) means that one metal is giving up electrons to another (anode to cathode), meaning corrosion. Many "neglected" aftercoolers basically "weld" together (the various parts) ending up requiring replacement (and if made from "unobtainium" could be impossible to replace - they are expensive items). With many brands of aftercoolers, this corrosion happens even if the engine anodes are "looked after". Tony has a maintenance procedure (involving grease) that helps to reduce and/or prevent this corrosion (at least in aftercoolers that able to be disassembled). Lots of good info on his site.

Disclosure: I am not in any way associated with Tony or his company other than being a small customer (from time to time) and a grateful boater for all of his free info.

 

[Taras]

Good article on the benefits of Fresh Water Flushing.....
https://www.sbmar.com/articles/the-benefits-of-fresh-water-flushing-your-marine-diesel-engine/

 

[RickyD]

Some may find it interesting that my first trawler was a Lien Hwa 47 with Ford Lehman 275s I think. Maybe 375s, anyway the prior owner had replumbed the anchor washdown hose connection to freshwater flush the engines and to refill the water tanks. Then he also plumbed the fresh water tanks to do the same thing so he could flush the engines after a run to the Islands from on board water. Lots of confusing water lines to figure out on the new to me boat but it worked. The boat then needed a water maker which it never got. I would only flush at the dock. Later I plumbed in another salt water anchor wash down. I did not own the boat long enough to provide any useful information about zincs and the like. I do remember using bamboo skewers to "rod" out the heat exchangers. It appears that they weren't alway flushed with fresh.

 

[Comodave]

Some may find it interesting that my first trawler was a Lien Hwa 47 with Ford Lehman 275s I think. Maybe 375s, anyway the prior owner had replumbed the anchor washdown hose connection to freshwater flush the engines and to refill the water tanks. Then he also plumbed the fresh water tanks to do the same thing so he could flush the engines after a run to the Islands from on board water. Lots of confusing water lines to figure out on the new to me boat but it worked. The boat then needed a water maker which it never got. I would only flush at the dock. Later I plumbed in another salt water anchor wash down. I did not own the boat long enough to provide any useful information about zincs and the like. I do remember using bamboo skewers to "rod" out the heat exchangers. It appears that they weren't alway flushed with fresh.

They made a 275 but I don’t think there was ever a 375.

 

[DavidM]

I am late to this thread (and I haven't read all 83 posts so far) but I am a true believer in fresh water flushing the engine after every use in salt water. It is particularly useful on engines with after coolers because the salt water/intake air interface is protected by just an o ring and salt water left in them can destroy that interface and lead to big problems, even trashing the engine.

For most of the five years I owned a Yanmar 6LY powered Mainship Pilot 34, it was flushed or otherwise protected (see below) by flushing. I never pulled the after cooler to check as I started flushing right after servicing the after cooler and never thought I needed to.

There is some debate on what kind of protective anode should be used if you store it fully flushed for 95% of its life and use it only another 5% in salt water. Some would say use magnesium anodes as they are recommended for fresh water. The downside is that salt water may quickly waste them.

Otherwise protected- means the two years I kept it on a mooring up the Connecticut River in an area that was fresh water 95% of the time, but when I took it out in the Sound it was definitely exposed to salt water. I do know that my hull zincs lasted much longer in that situation.

David

 

[Comodave]

Use aluminum, it works everywhere.

 

[Art]

Use aluminum, it works everywhere.

I've yet to locate, hear-of or see where I can find qualified, scientifically conducted test reports on aluminum - vs - zinc and/or magnesium in salt, fresh and brackish waters.

Do you know where I can find reports such as that?

 

[Comodave]

Well, let me pull out my microscope…. Oh yeah, right, I am not the scientist. I can’t say that I can give you the absolute scientific facts you are looking for. Maybe someone else can. But Art, I have to ask. Why don’t you demand this level of data on every thread?

 

[Art]

Well, let me pull out my microscope…. Oh yeah, right, I am not the scientist. I can’t say that I can give you the absolute scientific facts you are looking for. Maybe someone else can. But Art, I have to ask. Why don’t you demand this level of data on every thread?

I don't demand... just wanna know the facts mam... ya know - sorta like Joe Friday on Dragnet!

The main item I don't understand: For many, many decades zinc and magnesium were the absolutely trusted and by far the most often used anodes of choice by boaters, metallurgists, shipwrights, boat yard owners, ferry lines, the navy etc, etc. Then all of a sudden [seemingly within the last few years] many began saying oh no, no, no the real best anode is aluminum. I'd just like to learn some facts; like some sort of backup tests having been done and documented.

That's not asking for much. Especially as seeing that anodes protect tens of thousand dollar equipment on boats!

EDIT: Dave, I sure do not want you to think I'm picking on you or anyone else for putting thumbs-up on aluminum as the best anode. But I do want to say. Recently I spoke with a very busy boat bottom guy who's been doing underwater maintenance on hulls for many years. I asked him what he thought about aluminum in salt water... or in freshwater. He said that he's not seen stats yet regarding how effective aluminum actualy is and until those stats become available he'll stick with zink in salt and mag in freah waters.

I'm seeking the facts mam... just the facts, Joe Friday

 

[rslifkin]

I'm pretty sure aluminum (actually navalloy, not pure aluminum) anodes weren't available as far back in history as zinc and magnesium. So their common usage is somewhat more recent.

 

[Comodave]

It has been recently that the Navy found some aluminum alloys that work better than zinc. Here is a write up on it. Maybe not the whole story but certainly part of it.

Aluminum anodes are rapidly replacing zinc for use on ALL hull materials. With the recent advent of alloys developed by the US Navy, anode aluminum is very different from the aluminum alloys used for boat hulls, outboards, and stern drives. These "mil spec" aluminum anodes are more electrically active and protect better than zinc, plus they last longer! Aluminum has been used in the offshore industry for years to protect installations where long-term corrosion protection is essential. Aluminum anodes also use a much less toxic activator – which makes them better for the environment. To top it off, aluminum anodes are really the only choice that will work in both brackish AND salt water. So if you keep your boat in a place that is exposed to both (such as at the mouth of a river that empties into the ocean) you should definitely be using aluminum. Aluminum has become the anode of choice for the US Navy, as well as for large commercial fleets. This is due to the money they save (aluminum anodes last longer so ships go longer between replacements) and because aluminum is so much lighter that they can help provide better fuel economy in larger fleets. Aluminum anodes are available for both recreational and commercial applications.