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Old 02-12-2011, 05:53 PM   #1
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Fresh Water Flush Your Engines?

Hi All,
About 3 years ago I installed a fresh water flush system for all of my engines ( 2 mains and 2 gen sets).
What I did was to tap into the top of the sea strainer, screwed in valve and then ran a fresh water hose to the top of each of the 4 sea strainers.* Now when I am done with a cruise, I simply shut off the sea valve, turn on the fresh water and let the engines run for a few minutes to fully flush the engines raw water system.
After doing this for 3 years, I have not had to replace any*the numerous engine zincs or worry about having to boil out the heat exchangers.

After watching my friend spend a lot of money on replacing his heat exchangers due to corrosion, I just wonder why they don't make this standard equipment on salt water vessels?

Does anyone else have a fresh water flush system?

Steve
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Old 02-12-2011, 06:04 PM   #2
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RE: Fresh Water Flush Your Engines?

Steve-
I don't, but I sure like your idea. I try to rinse my dink engine in fresh water when we get to the slip- why not the rest. Do you have Groco sea strainers? Any pics?
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Old 02-12-2011, 07:07 PM   #3
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RE: Fresh Water Flush Your Engines?

Quote:
Taras wrote:

Hi All,
About 3 years ago I installed a fresh water flush system for all of my engines.* After doing this for 3 years, I have not had to replace any*the numerous engine zincs or worry about having to boil out the heat exchangers.

After watching my friend spend a lot of money on replacing his heat exchangers due to corrosion, I just wonder why they don't make this standard equipment on salt water vessels?

Does anyone else have a fresh water flush system?

Steve
Can vouch for a fresh water flush system greatly extending zinc/heat exchanger maintenance/service life.*

Installed the first one on my wooden 40' Ed Monk Sr. classic after repowering in 1980.* Sold that boat in 1997 without any cooling system issues.

Bought the current boat in 1997, and could see there had been salt water corrosion in the cooling systems of both the ME and genset.* For the ME, as you did, I drilled*a hole in the raw water stainer and mounted a valve and hose connection.* For this application, it is very easy to bring the hose to the strainer after washing the boat, so did not have to run any internal FW supply.

For the generator which is located near the fresh water tanks, I tapped in to the cooling line between the thru-hull and strainer, the FW supply comes unpressurized from the fresh water tanks.* This setup allows me to easily drain the FW tanks by running the generator which provides regular turn over of fresh water.

It is difficult to quantify the level of improvement to the cooling systems by installing a FW flush, but I would guess that it easily extends most maintenance chores by 2-3 times.* Of course, a lot of this depends on how much the boat is used/tied up, along with consideration of moorage in fresh or brackish water.

I'm not aware of any production boats that come with*a FW flush.* It's a great owner add-on.
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Old 02-13-2011, 05:21 AM   #4
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RE: Fresh Water Flush Your Engines?

"Can vouch for a fresh water flush system greatly extending zinc/heat exchanger maintenance/service life. "


It extends the ZINC life because in fresh water zinc is not effective.


Save the zinc , loose the heat exchanger?

Magnesium is the protection in fresh water , in the engine or on the hull.
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Old 02-13-2011, 09:00 AM   #5
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RE: Fresh Water Flush Your Engines?

Hi David,
I finally joined boatdiesel but have'nt been there much yet.
How long do most heat exchangers last?
One shouldn't run the fresh water hose very long without running the engine as the lift mufflers can fill up and flood the engine through the exhaust valves.
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Old 02-13-2011, 09:46 AM   #6
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RE: Fresh Water Flush Your Engines?

Quote:
FF wrote:

"Can vouch for a fresh water flush system greatly extending zinc/heat exchanger maintenance/service life. "


It extends the ZINC life because in fresh water zinc is not effective.


Save the zinc , loose the heat exchanger?

Magnesium is the protection in fresh water , in the engine or on the hull.
In my current engine, the heat exchanger zinc*does not remain immersed after the engine is shut down.* The zinc is replaced based on engine hours.* But I observe less salt water effect/corrosion on the sea water pump which remains immersed in FW.* The engine remains bonded to the underwater zincs.

*
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Old 02-13-2011, 09:54 AM   #7
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RE: Fresh Water Flush Your Engines?

Quote:
nomadwilly wrote:

One shouldn't run the fresh water hose very long without running the engine as the lift mufflers can fill up and flood the engine through the exhaust valves.
Eric,* forgot to mention that I run the engine while flushing.* But I don't have a lift muffler, so could theoretically flush with using only FW system water pressure.* But at my moorage, water pressure is very high, and it has to push past the sea water pump.*

So the best solution for my application is to run the engine for a few minutes while flushing.* I leave the thru-hull valve open, so the cooling system does not become pressurized.* The fresh water supply is greater than the supply needed for the engine to run at idle, so everything ends up being fresh water.

*
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Old 02-14-2011, 03:44 AM   #8
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RE: Fresh Water Flush Your Engines?

"Fresh water is much less corrosive with or without zincs or magnesium anodes and zincs do some good in fresh water, but not as good as magnesium."


The Zinc is to slow down Electrolisis , not sludge , or salt corrosion on metal.
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Old 02-14-2011, 04:17 AM   #9
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RE: Fresh Water Flush Your Engines?

What is boatdiesel?
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Old 02-18-2011, 05:02 PM   #10
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RE: Fresh Water Flush Your Engines?

FF,
You are more knowledgeable about this topic than me, but I have owned Fresh Water boats my whole life and have never had any corrosion issues with any of them.*

By fresh water flushing the*engines of the salt water vessel I have now, I have been able to avoid replacing the large number of zincs on my engines and have been able to avoid over heating issues with the heat exchanger.* With all the maintenance on a boat, this is one less thing I have to worry about.* I am very pleased with what Fresh Water flushing has provided.

Steve
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Old 02-19-2011, 03:28 AM   #11
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RE: Fresh Water Flush Your Engines?

but I have owned Fresh Water boats my whole life and have never had any corrosion issues with any of them.

Perhaps the dockside power was in better condition , or the past boats electrics were better done?

Electric dumped in Fresh water can kill, people or gear , just as sea water can.
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Old 02-22-2011, 08:37 AM   #12
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RE: Fresh Water Flush Your Engines?

I installed a fresh water flush after purchasing my boat last May. I never used it because it is docked in fresh water. I finally had a chance to use it this last weekend as we moved the boat to a salt water location. Shortly after the purchase I had to change the raw water pump on the port engine.

Last weekend as I was flushing the engine my routine is to hook up the hose to the top of the strainer but not turn it on. I start the engine and then turn on the hose. I then slowly close the engine thru hull valve and flush the engine. I did the stbd engine first and it worked perfectly. Ran the flush for about 5 minutes.


Did the port engine in the same manner, got it started and went to the bridge to check on something else. Came back 2 minutes later and found the hose leading to the strainer collapsed and thus very little water getting to the engine. I immediately shut the engine down and turned the water off, with hopefully no damage to the impeller.


What happened is the port engine with the new raw water pump is pulling more water that the hose can supply, so it collapsed. The fix is to find a hose that doesn't collapse and to never take my eye off the hose as the engine is running.


I think Tony on boatdiesel.com has said the single most important thing you can do to extend the life of your engine is to install a fresh water flush and to ensure that it is not overpropped.


Done
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Old 02-23-2011, 05:01 PM   #13
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Fresh Water Flush Your Engines?

Quote:
timjet wrote:

*
I think Tony on boatdiesel.com has said the single most important thing you can do to extend the life of your engine is to install a fresh water flush and to ensure that it is not overpropped.
If your engine is cooled by it's own supply of coolant (anti-freeze) and that's the only thing that circulates through the engine, how does flushing the raw water system with fresh water extend the life of the engine?* I can see that perhaps it extends the life of the lube oil, transmission fluid, and engine coolant heat exchangers and the exhaust components that have raw water pumped through them, but how will it affect the engine itself?

If one has raw water cooled engines where salt water is pumped into the boat, through the actual engine*block and head**and out with the exhaust I can see it.* But I don't see how installing a fresh water flush on our boat with its*closed-loop engine cooling using diesel engine coolant (Cat brand*in our case)*would make one iota of difference to the life of our diesels.

*


-- Edited by Marin on Wednesday 23rd of February 2011 07:02:26 PM
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Old 02-23-2011, 08:23 PM   #14
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RE: Fresh Water Flush Your Engines?

Quote:
Marin wrote:I can see that perhaps it extends the life of the lube oil, transmission fluid, and engine coolant heat exchangers and the exhaust components that have raw water pumped through them, but how will it affect the engine itself?
Whew! I don't feel so stupid afterall. My thoughts exactly.

*
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Old 02-23-2011, 09:51 PM   #15
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RE: Fresh Water Flush Your Engines?

Quote:

timjet wrote:

*I think Tony on boatdiesel.com has said the single most important thing you can do to extend the life of your engine is to install a fresh water flush and to ensure that it is not overpropped.
Perhaps taken out of context, I think that Tony was talking about*hard run engines where heat exchangers/sea water cooling systems play a critical role in engine service life.**Fresh water flush helps in providing relatively clean sea water cooling system components and extends needed maintenance intervals.*

BoatDiesel regularly has threads about overheated engines, mostly due to overpropping and lack of cooling system maintenance.
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Old 02-24-2011, 05:44 AM   #16
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Fresh Water Flush Your Engines?

Quote:
Marin wrote:
If your engine is cooled by it's own supply of coolant (anti-freeze) and that's the only thing that circulates through the engine, how does flushing the raw water system with fresh water extend the life of the engine?* I can see that perhaps it extends the life of the lube oil, transmission fluid, and engine coolant heat exchangers and the exhaust components that have raw water pumped through them, but how will it affect the engine itself?

I will be the first to admit that I'm no expert and I don't think I took any one's comments out of context.

Marin, what you just described, oil cooler, heat exchanger, after cooler, exhaust components, tubo and related plumbing is the cause of most of the failures associated with high output low weight diesel engines. At least cruising the Cummings forum on boatdiesel.com seems to support this.

Additionally, those folks that run these engines at near their max rpm must take much closer attention to raw water pumps, alternators, idler pulley's and anything else that spins routinely at nearly 3000 rpm perhaps much higher when you factor in the pulley ratios.

I don't see many comments on these forums related to failures of internal components like pistons, valves, crankshafts, bearings, rings and related.

But it just makes sense to flush out the raw water system. If it didn't matter why not just send raw water into the cooling chambers of the engine instead of coolant.

But your comment: If your engine is cooled by it's own supply of coolant (anti-freeze) and that's the only thing that circulates through the engine, how does flushing the raw water system with fresh water extend the life of the engine? It doesn't,* it just extends the life of all the other components for the same reason using coolant in the engine extends the life of the engine block, head and everything else that comes in contact with coolant. A turbo for a Cummins costs upward of 2K and an after cooler probably as much or more.

*


-- Edited by timjet on Thursday 24th of February 2011 09:45:43 AM
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Old 02-24-2011, 08:02 AM   #17
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RE: Fresh Water Flush Your Engines?

However if your engine has simply a heat exchanger and perhaps oil cooler then a fresh water flush though still an easy way to extend the life of these components would not be as important.

Don't you flush your dingy outboard?
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Old 02-24-2011, 08:46 AM   #18
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RE: Fresh Water Flush Your Engines?

Don't you flush your dingy outboard

I never have as right now it sits ON the dink on davits. I flush at the end of the season only.
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Old 02-24-2011, 10:57 AM   #19
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RE: Fresh Water Flush Your Engines?

Quote:
timjet wrote:

Don't you flush your dingy outboard?
Sure, after every cruise if we use the dinghy.* But the salt water cools the outboard's*engine block itself.* Letting an outboard sit with salt water or salt residue in the engine's cooling passages is probably not a good idea.

I dont' deny that a fresh water flush might extend the life of the raw water cooled components of a marine*diesel engine--- raw water pump, heat exchangers, and exhaust components.* But that's not extending the life of the engine, just the ancilliary hardware.* Important ancilliary hardware, no question, but all of it is usually pretty easily changed if necessary.

I just object to the implication that not running fresh water though one's raw water cooling system is going to somehow shorten the life of your engine.* It can't because there is never any salt water in the engine.* If there is one has a much larger problem than a fresh water flush will fix
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Old 02-24-2011, 12:32 PM   #20
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RE: Fresh Water Flush Your Engines?

Quote:
Marin wrote:
I dont' deny that a fresh water flush might extend the life of the raw water cooled components of a marine*diesel engine--- raw water pump, heat exchangers, and exhaust components.* But that's not extending the life of the engine, just the ancilliary hardware.* Important ancilliary hardware, no question, but all of it is usually pretty easily changed if necessary.
Marin,

You are of the opinion that the raw water cooling portion of your power plant is not considered part of your engine. In which case flushing the raw water portion of your power plant will not extend the life of the rest of the engine.
No argument here unless raw water makes it's way into the cylinders due to a corroded after-cooler or turbo.


I will however disagree with your opinion that the raw water portion of the engine is usually pretty easily changed if necessary. Maybe pretty easy for a diesel mechanic, and very expensive for the owner.


But a normally aspirated engine without after coolers, fuel coolers, and turbo's is a very different engine.*

*
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