Exhaust elbow.. when to remove and clean?

[Nostrodamus]

Our friend with the problems has a moody and the exhaust comes out below the waterline so you cannot see if water is coming out with the exhaust.
He thought he had cleaned the elbow when the problems arose. A mechanic looked at it and said that he had only half cleaned it. What he thought was thick walls was more crud.

 

[DaveRo]

The Yanmar YM operating manual says 'periodically operate the engine at near maximim RPM while underway'. Today I tried 3000rpm for 5 minutes (max is 3600). The overheating alarm came on. The sea tempetature was 28° however. Earlier YMs used to overheat in the Med. And I do wonder whether the hull raw water input on the Jeanneau restricts the flow.
Bizarrely, the engine hours meter, which hadn't worked for a year or more, started working again - briefly!

 

[Interlude]

The Yanmar manual also says that when you are finished with the engine, let it idle for 5 mins then rev to full revs four times before shutting down. I have found one other owner who does this, but having had to put a new elbow on my old 1GM-10, I follow the procedure with my 3YM-20.

 

[Skylark]

At the end of each season, when I'm in the slings, I run a bucket of diluted antifreeze through the raw water strainer.

My MD2030 now has 820 hours logged and I'm aware of the exhaust elbow issue. This thread is, as ever, informative and helpful. I like the idea to monitor the temperature with an infrared thermometer.

What does the panel think about running a bucket of diluted acetic acid (vinegar) through the raw water system from time to time? Would it dissolve any of the crud, cause harm, or simply not worth the bother?

 

[sam_uk]

I inherited a old volvo MD5C that had a overheating problem. On advice of a mechanic I ran brick cleaner (dilute hydrochloric acid) through the cooling system several times, left it in for a couple of hours, then ran the engine hard.

It completely solved the overheating problem.

 

[Heckler]

At the end of each season, when I'm in the slings, I run a bucket of diluted antifreeze through the raw water strainer.

My MD2030 now has 820 hours logged and I'm aware of the exhaust elbow issue. This thread is, as ever, informative and helpful. I like the idea to monitor the temperature with an infrared thermometer.

What does the panel think about running a bucket of diluted acetic acid (vinegar) through the raw water system from time to time? Would it dissolve any of the crud, cause harm, or simply not worth the bother?

David
the crud is as hard as bullets, vinegar wont touch it, take the elbow off, its pretty easy and have a look inside, will give you a hand if you like.
Stu

 

[sam_uk]

David
the crud is as hard as bullets, vinegar wont touch it, take the elbow off, its pretty easy and have a look inside, will give you a hand if you like.
Stu

Or brick acid will do it in situ.. Worth getting off every couple of years anyway I guess to check for corrosion.

 

[Nostrodamus]

Can anyone tell me what is the normal operating temperature of a diesel engine (Volvo MD 22)

 

[cmedsailor]

At the end of each season, when I'm in the slings, I run a bucket of diluted antifreeze through the raw water strainer.

My MD2030 now has 820 hours logged and I'm aware of the exhaust elbow issue. This thread is, as ever, informative and helpful. I like the idea to monitor the temperature with an infrared thermometer.

What does the panel think about running a bucket of diluted acetic acid (vinegar) through the raw water system from time to time? Would it dissolve any of the crud, cause harm, or simply not worth the bother?

As Stu said the crud is very very hard. It really feels like steal.
I have just removed mine (11 years old boat, around 2.200 hours on the engine, never removed the elbow in the past, and as you know same boat as yours but in a different sea!), not because it was giving me any warnings but because of planning a very long trip this summer so I wanted to replace it with a new mixing elbow. Suprisingly it doesn't look that bad. I will see if I can manage to clean it a little bit and keep it as a spare in case of emergency. Not a difficult work to remove either.

 

[charles_reed]

On seawater cooled boats the exhaust elbow seems to be one part to keep your eye on.
A friend here has had to sail without an engine for a while as each time he turned it on it quickly overheated. When he took the elbow off it was completely blocked and it took some shifting.
I imagine that a blocked elbow will cause real problems and he was lucky not to damage his engine.
So how often should they be checked or removed for checking.

While we are on the subject do you also remove your non return valve to the engine (those upside down "U" things same as you may find on the toilet pipes. Can they be cleaned or do you replace them. For a bit of plastic they are very expensive.

Thanks for any replies/

Yanmar recommend removing and cleaning the exhaust elbow every 1000 hours - this applies to indirect-cooled engines as well as raw-water. It's probably a good idea to have a replacement to hand ( a local fabricator can make one foe 10% of the manufacturer's price) as they do need to be cleared mechanically and, whether stainless fabrication or cast iron, it's all too easy to put a tool through the wall.
The anti-siphon valve to which you refer is one of the methods used to prevent exhaust water being drawn into the manifold. The alternative (far less prone to malfunction) is the tube overboard.
The inverted U needs cleaning each big service - it comes off and needs to be cleaned in fresh water (I use sulphamic acid to clear deposits). Points of failure are the internal spring and the neoprene valve - I also replace the sealing O-rings.
As you say they are very expensive for what they are!!!

 

[vyv_cox]

What does the panel think about running a bucket of diluted acetic acid (vinegar) through the raw water system from time to time? Would it dissolve any of the crud, cause harm, or simply not worth the bother?

Complete waste of time and money. The acetic acid content of vinegar is very low, around 2% I think. Even if you flushed through with neat vinegar it would not do much for you. We used to clean salt and seawater deposits from components before examining them. Using far stronger acetic acid solutions we left them overnight, by which time if we were lucky the deposits were dissolved. Hydrochloric acid is considerably more effective when the deposits are still soft but once they are baked hard mechanical methods are the only way.

 

[jwilson]

What constitutes slow/cool running? I'm usually happy to achieve 5kts SOG and unless we're powering into waves that's usually 2000-2200 rpm with my Yanmar 3YM30 (Jeanneau SO35). Is that slow/cool?

I'm supposed to inspect the exhaust elbow (it's plastic) annually but so far I've failed to get the pipes off and haven't persisted for fear of breaking something - spares being not readily obtainable at short notice in Greece. (It's 7 years old and done about 850 hrs.)

I have exactly the same boat/engine. As others have said the plastic lump is not the exhaust elbow but the waterlock, the exhaust elbow is the metal bit resembling this - http://www.frenchmarine.com/product/Yanmar-128370-13530-Elbow-Mixing-1263-45 that attaches to the aft top of the engine. I replaced mine last year at 7 years old as a precaution as the inside was looking a bit corroded rather than clogged. They are poorly made bits of welded steel, and not something you want to fail - hot exhaust and salt water spraying around inside the engine compartment. Again, as others have said, slow running is worse for them than hard use.

With the same engine/boat I personally find 2,000 rpm pointlessly slow: I'm happy to sail slower but if the engine has to be on it's because I want to get somewhere. I regard 2,600 to 2,800/3,000 rpm as cruising revs, and I occasionally use full throttle at 3,400 for a minute or two. You are not damaging your engine though at 2,000-2,200, as long as it is run for a good long time to get properly hot most of the time.

Does your 3YM30 overheat if run at over 3,000 rpm for more than five/ten minutes? Mine has done so intermittently from the day it passed about 100 hours running, and Yanmar changed the heat exchanger early on under warranty for one with more tubes. It improved the situation but has never totally cured it. If it does overheat a minute at 1,500 rpm cools it down and the alarm goes off, and you can go back to 2,900. It has been checked with a thermometer, and it is overheating, not just the alarm setting wrong. If you search on the web you can find other 3YM30 owners with the same problem, often in SO35s or US Hunter 36s.

 

[vyv_cox]

Can anyone tell me what is the normal operating temperature of a diesel engine (Volvo MD 22)

Finding the figure for your engine via Google seems difficult. although I found several sites that quote the thermostat opening temperature for Volvos I could not find one for yours. So generically I would say for an indirectly cooled engine 85C or thereabouts. For a directly cooled about 70C to minimise salt deposition.

 

[Nostrodamus]

Finding the figure for your engine via Google seems difficult. although I found several sites that quote the thermostat opening temperature for Volvos I could not find one for yours. So generically I would say for an indirectly cooled engine 85C or thereabouts. For a directly cooled about 70C to minimise salt deposition.

Thanks Vyv.. I have been having the same problem finding a temp. Depending on where you look diesel engines seem to work between 85-95. Does the temperature of sea water have much effect on engines?

 

[vyv_cox]

Thanks Vyv.. I have been having the same problem finding a temp. Depending on where you look diesel engines seem to work between 85-95. Does the temperature of sea water have much effect on engines?

Provided that the heat exchanger was designed for any expected temperatures the thermostat should control to the design figure. With an International company like Volvo one would hope that was so, always providing that the HE is not fouled.

Brings back memories of some desert locations I have worked in, where air cooled heat exchangers could not cope with ambients of 50C plus. Operators would spray the machines with water (at who knows what cost of production) which fixed things in the short term but often brought severe corrosion problems later on, machinery rarely being designed to operate permanently soaked. Worse still in tropical locations, where they sprayed seawater.

 

[Tranona]

At the end of each season, when I'm in the slings, I run a bucket of diluted antifreeze through the raw water strainer.

My MD2030 now has 820 hours logged and I'm aware of the exhaust elbow issue. This thread is, as ever, informative and helpful. I like the idea to monitor the temperature with an infrared thermometer.

What does the panel think about running a bucket of diluted acetic acid (vinegar) through the raw water system from time to time? Would it dissolve any of the crud, cause harm, or simply not worth the bother?

Apart from the lack of effectiveness of acetic acid, you are confusing two issues. The build up of deposits in exhaust elbows is little to do with the cooling seawater. The main cause is running the engine too cool from either short runs or running at too low revs. So the deposits are mainly carbon build up. If you have seawater related cooling problems this is more likely to be clogged heat exchanger tubes, which can be physically cleaned. The freshwater system is kept clean by using the correct coolant.

Raw water cooled engines are different and waterways can clog up with salt deposits, and in this case cleaners such as brick cleaner can be effective in clearing the water passages.

The answer with engines like yours (same as mine) is to run them hard and long enough to get up to working temperature. My engine has done 3500 hours and the exhaust elbow has never been touched. So far no signs of any trouble.

 

[Bosun Higgs]

On seawater cooled boats the exhaust elbow seems to be one part to keep your eye on.
A friend here has had to sail without an engine for a while as each time he turned it on it quickly overheated. When he took the elbow off it was completely blocked and it took some shifting.
I imagine that a blocked elbow will cause real problems and he was lucky not to damage his engine.
So how often should they be checked or removed for checking.

While we are on the subject do you also remove your non return valve to the engine (those upside down "U" things same as you may find on the toilet pipes. Can they be cleaned or do you replace them. For a bit of plastic they are very expensive.

Thanks for any replies/

I would not routinely remove the exhaust elbow since you can get into all sorts or irritatring problems to do with seized bolts, corroded faces ( Volvo 2003 for example) and make life worse for yourself. The ideal is to keep an eye on the engine and to react straight away when you get a problem. But then I have never kept a boat for more than a few years and maybe if I were keeping one for 15 years I would think differently.

The non return valve gets sorted every year. In my boat the previous owner replaced the valve part of the U thingy with a short length of plastic pipe and one of the whales non return valves. Works OK and is cheap.

 

[Skylark]

Apart from the lack of effectiveness of acetic acid, you are confusing two issues. The build up of deposits in exhaust elbows is little to do with the cooling seawater. The main cause is running the engine too cool from either short runs or running at too low revs. So the deposits are mainly carbon build up. If you have seawater related cooling problems this is more likely to be clogged heat exchanger tubes, which can be physically cleaned. The freshwater system is kept clean by using the correct coolant.

Raw water cooled engines are different and waterways can clog up with salt deposits, and in this case cleaners such as brick cleaner can be effective in clearing the water passages.

The answer with engines like yours (same as mine) is to run them hard and long enough to get up to working temperature. My engine has done 3500 hours and the exhaust elbow has never been touched. So far no signs of any trouble.

This is helpful, thanks. I wasn't intentionally confusing two issues, I hadn't realised that the crud deposit was carbon, I thought it was salt deposit. Now I've learned something.

I'm not aware that I do have a problem, I was mainly looking for preventative advice, hence my query re acetic acid. Last season, I had a rust stained weep from the elbow / hose joint. I cleaned the exterior surface of the elbow and replaced the hose (ouch, they're expensive). It wasn't possible to assess any internal build up and I'm a big believer in "do no harm" so I did not remove it / risk seizing bolts, leaking joint faces and so on.

 

[Stork_III]

Interesting, I wonder if Volvo Penta have the same advice?

From VP Owner'sManual

Cruising Speed

Operating the engine at WOT should be avoided since it is uneconomical and uncomfortable. Volvo Pents recommends a cruising speed 300-500 rpm below max revs at WOT.

WOT for MD2010-2040 - 3200 to 3600.

 

[DaveRo]

Yanmar recommend removing and cleaning the exhaust elbow every 1000 hours...

250hrs/1yr on my 3YM30.

Does your 3YM30 overheat if run at over 3,000 rpm for more than five/ten minutes? Mine has done so intermittently from the day it passed about 100 hours running, and Yanmar changed the heat exchanger early on under warranty for one with more tubes. It improved the situation but has never totally cured it. If it does overheat a minute at 1,500 rpm cools it down and the alarm goes off, and you can go back to 2,900. It has been checked with a thermometer, and it is overheating, not just the alarm setting wrong. ..

It did recently - see my subsequent post. Since I don't normally rev it that high I don't know if it always happens - and I'm not going to try it again. My engine was built after the change to the heat exchanger.