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Old 19-04-2015, 23:58   #1
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Flushing A Seawater Cooled Engine?

done a bit of a search but couldnt find much - an old Yanmar expert told me to flush the engine via the input hose with a bucket of 5% ish dilution of hydrochloric acid every couple of years. I did it a few years ago but I dont really fancy doing it again - is there any other way to clean salt and buildup out of the water galleys? I came back from a month away recently and the main feed into the engine had silted up and concreted, sending all water to the startup by-pass - had to give it a good poking with a bit of wire to get water into the engine again. The eng. is a yanmar 2qm20, I pulled the anode galleys and she doesnt look too bad inside, there doesnt seem to be so much crap buildup if you change the anodes fairly frequently, but the blockage to the engine has me a bit worried.
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Old 17-06-2015, 18:11   #2
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Re: Flushing A Seawater Cooled Engine?

I am interested in this topic and noticed no input,
any takers out there who has info or comments?
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Old 17-06-2015, 18:43   #3
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Re: Flushing A Seawater Cooled Engine?

I used to have a seawater cooled engine. About 1.5 years into my ownership it seemed like the temps were getting too high so I flushed it with Rydlyme and it seemed to help.

RYDLYME Marine: The Ultimate Biodegradable Marine Descaler! | RydLyme Marine

If you're not crazy about that particular product just google up marine descaling. Since most engines these days are not seawater cooled most products are more commonly geared towards cleaning out large industrial type heat exchangers. Same basic principals apply.

No matter what you get read the label thoroughly and use accordingly.
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Old 17-06-2015, 18:56   #4
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Re: Flushing A Seawater Cooled Engine?

Hi

We had a seawater cooled Bukh 36 hp for 18 years and used to flush it by filling the block with white vinegar and letting it stand overnight and then running the engine again to flush out.

White vinegar is cheap and not so aggresive as acid. By doing this proceedure annually we kept all the innards free from salt build up.

We rebuit the engine after 11,000 hours and got 20,200 hours on the engine before we replaced it. Good maintenance should give you long life.

Best wishes.
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Old 17-06-2015, 19:10   #5
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Re: Flushing A Seawater Cooled Engine?

great info
thanks
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Old 18-06-2015, 00:55   #6
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Re: Flushing A Seawater Cooled Engine?

I used vinegar on my 3GM30 Yanmar a number of times. Used a small bilge pump in a bucket with a return hose from the exhaust manifold to circulate it around for an hour or two, appeared to work well from the amount of gunk the vinegar picked up.
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Old 18-06-2015, 06:24   #7
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Re: Flushing A Seawater Cooled Engine?

I once fixed an overheating engine on a delivery by running a 50% dilution of muriatic acid into the system, letting it sit for about 10 minutes, and flushing it out thoroughly.
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Old 18-06-2015, 06:41   #8
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Re: Flushing A Seawater Cooled Engine?

I've recently used Rydlyme to flush the raw water side of our freshwater cooled main engines and genset. The mains were actually in good shape before I started, but the heat exchanger on the genset (3-cyl Yanmar engine) needed some TLC and the product seems to have done a good job.


Presumably that kind of product would work for a seawater cooled engine, and presumably other similar products would work equally well.


There are two basic technique: fill-wait-flush, or recirculate. Latter slightly depends on if you can identify easy innies and outies, if you have a decent pump, etc. I'd imagine there may be other issues trying to use that technique on a seawater cooled engine.


I tried recirculation on one main, fill-wait-flush on the other... and noticed no difference in outcome. OTOH, the mains were in good shape going into the project.


I used fill-wait-flush on the genset, primarily because it's a simpler system (pretty much just the heat exchanger) and it was easier than pulling hoses off to set up a recirculation path.


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Old 18-06-2015, 07:05   #9
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Re: Flushing A Seawater Cooled Engine?

I cleaned the scale out of my air conditioner unit recently, using the Barnacle Buster solution. Prior to cleanout it was giving a high pdf alarm and shutdown that Cruisair said was probably due to buildup in the circulation tubes. I diluted the BB according to the instructions, and then pumped it thru the system using a siphoning-type pump. They recommended 12 hrs of soak time, if not circulating. I let it sit a couple of hours, but then pumped thru new solution and displaced the old just because I had extra in the bucket, and wanted to see what would come out. It was nasty, black, had sediment in it. It clearly did its job. At the end of the 12 hrs, I pumped new stuff thru again, but the fluid in the tubes came back looking like the clean BB solution I had pumped thru hours before. So it looked like it had done most of the work in the first couple of hours. If that makes sense.

Anyway they recommend BarnacleBuster for seawater cooling systems as well. And it is enviro-friendly enough that they say it can be pumped overboard.
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Old 18-06-2015, 15:28   #10
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Re: Flushing A Seawater Cooled Engine?

Quote:
Originally Posted by RaymondR View Post
I used vinegar on my 3GM30 Yanmar a number of times. Used a small bilge pump in a bucket with a return hose from the exhaust manifold to circulate it around for an hour or two, appeared to work well from the amount of gunk the vinegar picked up.
Did you remove the thermostat and/or the anodes first?
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Old 20-06-2015, 18:26   #11
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Re: Flushing A Seawater Cooled Engine?

I find lots of (often conflicting) advice on how best to flush ... but nothing on how often flushing should be done.

I'm a believer in preventative maintenance, not wanting to wait until engine performance (or lack thereof) demands it, so can any experts tell us what is appropriate?

Thanks - Rusty
(pair of 3GM30's)
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Old 20-06-2015, 19:07   #12
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Re: Flushing A Seawater Cooled Engine?

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Originally Posted by sapient sue View Post
Hi

We had a seawater cooled Bukh 36 hp for 18 years and used to flush it by filling the block with white vinegar and letting it stand overnight and then running the engine again to flush out.

White vinegar is cheap and not so aggresive as acid. By doing this proceedure annually we kept all the innards free from salt build up.

We rebuit the engine after 11,000 hours and got 20,200 hours on the engine before we replaced it. Good maintenance should give you long life.

Best wishes.
This sounds pretty good to me - it's now on my maintenance list.

As to the question of how often - my expert guy was fairly specific - every couple of years - ie 2 years - from experience that seems about right too.
The effect of a longer exposure to vinegar on the zincs wouldnt be much different to a shorter exposure to a stronger acid - ie not much if you're replacing the zincs as often as necessary.
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Old 21-06-2015, 06:19   #13
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Re: Flushing A Seawater Cooled Engine?

Citric acid can also be used to flush the engine. It is what MB uses in their diesel engines. You can buy citric acid as a dry powder on ebay. I used a bunch of this in my raw water Volvo and it cleaned out a bunch of gunk.

Shawn


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Old 21-06-2015, 13:47   #14
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Re: Flushing A Seawater Cooled Engine?

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Originally Posted by rgesner View Post
I find lots of (often conflicting) advice on how best to flush ... but nothing on how often flushing should be done.

I'm a believer in preventative maintenance, not wanting to wait until engine performance (or lack thereof) demands it, so can any experts tell us what is appropriate?

I haven't found great authoritative advice on that, although I think it might be find-able for your particular engine.

In our case, for example, the (Kohler) Service Manual says "flush and refill the cooling system at the interval listed in the operations manual's service schedule." And of course I don't have that manual, haven't found one yet. (or maybe I don't have a softcopy, and didn't remember to check the hardcopy... if I have that.) And of course that statement is about the freshwater side; the Service Manual is silent about the raw water side.

Anyway... I can tell you I did just descale the heat exchanger on our genset (Yanmar TNE74 engine). It has been in service for coming on 13 years now (approx. 925 hours), without descaling. An inspection camera confirmed it was time... that was an empirical test. After flushing, the inspection camera suggests descaling was a good idea.

I suspect 13 years service -- and it was still running fine -- suggests once/year is way too often. Once every 13 years seems OK. Unless other symptoms suggest otherwise -- loss of water flow, overheating, etc. -- maybe somewhere in the middle is better.



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Old 21-06-2015, 17:07   #15
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Re: Flushing A Seawater Cooled Engine?

The question of how often to clean the engine - it seems to me the problem is not really with salt scale build up but with collection of the by-product of the anodes corroding. If the engine is being used frequently this will be flushed out but if there are longer periods when the engine is not used the white gunk builds up and solidifies - which was what caused my recent problem. Actually, my old engine guy told me not to bother replacing the rear anodes because of this - I decided to maintain all the zincs but to clean the galleys as a part of the anode maintenace cycle. They do generate a lot of stuff. The zincs seem to last about a year. I've not had problems running the engine at least once a week - which i need to do anyway to keep the barnacles from taking over the prop.
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