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Old 02-12-2015, 01:31 PM   #1
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Raw Water Flush

This seems like a good idea-- is it?

On every outboard I've owned I always flushed it with freshwater after running it in salt water. Does it not make sense to do the same on my Yanmar?

http://youtu.be/YdqVulR5STo
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Old 02-12-2015, 06:51 PM   #2
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I'd like to know, myself. Seems intuitive that getting salt out of most any mechanical system wouldn't hurt.
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Old 02-12-2015, 06:57 PM   #3
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Greetings,
Mr. 01. I can't see any downside other than the time and effort required to do it. It could prolong the life of your heat exchanger/coolers but by how much, I haven't a clue.
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Old 02-12-2015, 07:10 PM   #4
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I've been doing this for several years now. I can flush the engine and generator in less than 30 minutes. I would much rather have the coolers sitting in a bath of freshwater when the boat was idle than saltwater. The consensus on boat diesel.com is that flushing provides a substantial benefit in a saltwater environment.
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Old 02-12-2015, 07:12 PM   #5
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As I understand - it reduces the buildup within the coolers/heat exchangers. This increases the time between R&R of those devices. Just the man-hours to get to all 8 (I have twin Yanmars) is ridiculous. Especially frustrating are those mounted on the sides against the hull. Nearly inaccessible - especially servicing anything on my port side motor. So I added a fresh water flush as part of the repairs/servicing when I purchased her.

Frequently recommended if you are on the Boat Diesel website.
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Old 02-12-2015, 07:22 PM   #6
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Any problem with the way the guy in the video had it rigged up? I kind of wonder about that valve on the top of the sea strainer. Is that mounted in plastic?
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Old 02-12-2015, 07:24 PM   #7
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Quote:
Originally Posted by cardude01 View Post
Any problem with the way the guy in the video had it rigged up? I kind of wonder about that valve on the top of the sea strainer. Is that mounted in plastic?

Have a good friend that does the same thing with his. Just make sure you turn the water off first then engine so you don't risk hydro locking it. Looks like you used a thru hull and ball valve. Plan on adding the flush feature one of these days to the genny and AC.
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Old 02-12-2015, 07:28 PM   #8
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Hard to say how effective or necessary it is for each piece of equipment.

There are companies that sell additives for flushing systems as cool, fresh water doesn't do a good enough job according to them.

I tend to agree as many times I spray something down only to feel residue when done...yet warm, soapy water does the trick.

I do flush my outboard and prays it helps.

I also have opened plenty of saltwater engines and have seen normal rust yet no salt buildup.

So no absolutes from me...can't hurt but most don't and it's not salt buildup that's the problem...it's rust through and flushing don't guarantee elimination of salt film.
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Old 02-12-2015, 07:32 PM   #9
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As others have said, boatdiesel gurus, Tony Athens is particular, unequivocally recommends fresh water flushing. I installed one on my Yanmar 370 hp 6LY a year ago similar to the one shown on the video.

It works great. It extends engine zinc life 3-5 times. The sea water after cooler which is one of the most critical components on this engine can go for 3 times as long between servicing.

To flush my engine takes just 5 minutes. Hook up a garden hose to the ball valve on top of the strainer and turn on the water. Start the engine. Close the sea water thruhull valve. Run for 3-4 minutes. Shut off the water. Shut off the engine. Reopen the sea water thruhull valve.

I made mine up by drilling and tapping the strainer cover for a 1/2" female NPT. Screwed in a street elbow, a nipple, a valve and a hose fitting. Pic is attached.

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Old 02-12-2015, 07:36 PM   #10
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Is it tricky mounting the ball valve on the sea strainer?
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Old 02-12-2015, 07:38 PM   #11
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The setup in the video is close to what I use. I connect the hose to a 10 gallon bucket and to a modified strainer cap so the motor sucks the water at idle. I am leery of using pressure from a hose due to the potential for putting water in places you might not want it. The video does not make it clear whether the connections are permanent or used only for flushing. I use a spare top for my strainer that is plumbed for flushing. It is only used for flushing. When I have finished flushing, I put the original strainer cap back in place. If the user in the video leaves that modified strainer cap installed with the ball valve closed when not flushing, he risks a catastrophic failure if and when that modified strainer cap fails due to fatigue and vibration.
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Old 02-12-2015, 08:04 PM   #12
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That's what I was thinking-- vibration causing cracks. Or something falls on it or whatever.
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Old 02-12-2015, 08:04 PM   #13
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I use a slightly different set up. My Forespare through hull intake valves are three way units. The extra port is used for fresh water flush. I do not like to hook a dock hose directly to the cooling SX since many years ago I flooded a motor that way. So I run a hose into a big bucket and put a second hose from bucket to extra port on intake throw the valve handle and let the motor suck up water at idle. One of the reason second hand fresh water boats are so desirable is because they always get their engine flushed out with fresh water no mater what the previous owners attitude is toward the practice.
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Old 02-12-2015, 08:45 PM   #14
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Another great debate topic.....anyone have definitive proof it helps?

What components does it help? How?

Zinc lasting longer in fresh water is a foregone conclusion...the same as you don't put zinc on the outside of a boat in fresh water as they don't work well if at all.

Fresh water engines are no more desirable unless side by side with accurate maintenance logs. Freshwater boats are more desirable for a variety of reasons...yes less corrosion...but you really don't see where it is or isn't taking a toll on engine life.

Sure, I can see some engines with strangely engineered components like some after coolers may have a benefit, but I have not seen a fresh water flush universally suggested by a broad spectrum of engine experts.
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Old 02-12-2015, 08:59 PM   #15
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What if your engine has no zincs?
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Old 02-12-2015, 09:10 PM   #16
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Quote:
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What if your engine has no zincs?
That is either great or a mistake or you just dont see it and there's no manual to tell you?

...either way it is rare that a heat exchanger doesn't have one..and a over or two....but I am game that some engines may have either some electrical device to rep,ace zincs or just manufactured without any I mind.
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Old 02-12-2015, 09:32 PM   #17
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How about your exhaust elbow? Freshwater flushing can reduce the inevitable corrosion in that part. Depending on how your engine is installed. Parts of the raw water cooling system that are above the water line may drain of water, eventually building up a layer of salt on those parts. To each their own, but I think the few minutes it takes to flush motor at the end of a weekend is worth it. If I was a long distance cruiser, I might think otherwise.
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Old 02-12-2015, 09:40 PM   #18
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How about your exhaust elbow? Freshwater flushing can reduce the inevitable corrosion in that part. Depending on how your engine is installed. Parts of the raw water cooling system that are above the water line may drain of water, eventually building up a layer of salt on those parts. To each their own, but I think the few minutes it takes to flush motor at the end of a weekend is worth it. If I was a long distance cruiser, I might think otherwise.
Do you know for a fact the flush is actually getting all the salt off and that even a tiny bit isn't going to cause just as much corrosion?

That's the million dollar question in my mind.

There are parts like some outboard thermostats that definitely seem to avoid salt buildup if flushed well....but that's for buildup and not really corrosion.

I can't say that it hurts to fresh water flush...but for most engines and parts I have worked with....I can't definitively say it helps.
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Old 02-12-2015, 09:52 PM   #19
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Another great debate topic.....anyone have definitive proof it helps?

What components does it help? How?

Zinc lasting longer in fresh water is a foregone conclusion...the same as you don't put zinc on the outside of a boat in fresh water as they don't work well if at all.

Fresh water engines are no more desirable unless side by side with accurate maintenance logs. Freshwater boats are more desirable for a variety of reasons...yes less corrosion...but you really don't see where it is or isn't taking a toll on engine life.

Sure, I can see some engines with strangely engineered components like some after coolers may have a benefit, but I have not seen a fresh water flush universally suggested by a broad spectrum of engine experts.
I believe you are putting too much faith in the zincs, but better than nothing in salt water. Second the salts in sea water tend to crystalize in the cooling system and when bad enough clog things up ergo hot running or even cooked motor. Metal in general fares better in fresh water vs salt and your engine is made of what? Mechanics I have consulted so far have all agreed my fresh water motors will need much less maintenance of cooling system than if run in salt water. Many engines do not get recommended cooling system maintenance do to the difficulty and expense of that care. Fresh water run through the cooling sx and standing in it is much preferred rather than salt water standing and drying into solid salts. Salt water and a thing called marine age(the amount of time exposed to a salt water environment) are commonly considered in the health of a marine engine. In fresh water (you may know this but in case you don't )we use aluminum anodes and there is a trend to do this in salt water also.
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Old 02-12-2015, 10:27 PM   #20
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Raw Water Flush

I really don't think this engine ( Yanmar 4jh4-hte) has zincs. I can't find any, and no mention of them in the manual.

Looked it up on boatdiesel and some there have confirmed this. Sounds crazy I know. The apparent lack if zincs is what peaked my interest in flushing with fresh water.
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