Yanmar Exhaust Elbow

[nick8489]

I'm having my two yearly rant about the inadequacy of the design or fit for purpose of the Yanmar Exhaust Mixing Elbow (3YM30 on my 2004 H33)
The one shown below achieved 300 hours. I am trying a new cast aluminium one this time.

 

[kloudie1]

What is wrong with it, Nick? Can't see inside.. if it is plugged, you can carefully chip out the coke/salt deposits .. .. Cast aluminum.. interesting.. where is it available?

 

[nick8489]

Yanmar exhaust elbow photo

I'm having my two yearly rant about the inadequacy of the design or fit for purpose of the Yanmar Exhaust Mixing Elbow (3YM30 on my 2004 H33)
The one shown below achieved 300 hours. I am trying a new cast aluminium one this time.

Somehow the photo of the old elbow didn't get through

 

[kloudie1]

Oh! I see .. chipping on that isn't going to help much !

 

[Charles Erwin]

Please tell us where aluminum casting is available - and whether the aluminum purveyor is willing to stand behind his/their product.

Would be very interested to see comparison between aluminum and a simple unit made from schedule 80 black iron pipe fittings.

Charles

 

[Gunni]

My Yanmar 4JH3E came with an extruded/welded stainless steel mixing elbow. Less radical of a bend. 500 hours on the engine I checked it last fall and it was clean as a whistle. Go figure. Maybe you can find a SS elbow for your engine?

 

[Don S/V ILLusion]

Some years ago I had the opportunity to speak with 2 of the Yanmars design engineers about the two types of elbows they use. According to them, the cast elbows greatly outlive the stainless alloy type.
Having had both on different boats/engines, they were correct.

 

[Ralph Johnstone]

Mixing Elbow Problem

The one shown below achieved 300 hours. I am trying a new cast aluminium one this time.

I ***** and gripe about my elbow and manage to get about 3-4 years but I don't see the amount of corrosion you seem to have in there.

Your cast aluminum elbow sound interesting although I don't know how it will stand up to hot salt water and carbon. Do you have a web site for the aluminum elbow ?

Got to ask ............. in your first photo, is that a crack in the discharge or is it just the picture ?

 

[Bill Roosa]

Aluminum is a good alternative to zinc!!! just sayin
The old cast iron one didn't look that bad to me. Couple of minutes on a wire wheel and she would be good as new.
Now if you wanted to see bad..... I had an atomic 4 that........

 

[Steve Dion]

Nick:

I agree that yours looks bad, but 10 years and 300 hrs is not all that bad. I am curious on how you run your engine. Do you run it at low RPM's or are you running at 2500 - 3000 when motoring?

Our H'31 had several hundred hours on it and it never looked like yours. Our boat is in the California Delta so it does not have these issues like they seem to have in salt water.

Our current engine is a 3JH and it has about 400 hrs on it and there are no signs of coking either.

 

[nick8489]

Please tell us where aluminum casting is available - and whether the aluminum purveyor is willing to stand behind his/their product. Would be very interested to see comparison between aluminum and a simple unit made from schedule 80 black iron pipe fittings. Charles

I found it on eBay and the supplier is a company called Marina's Marina Inc in Barnegat NJ. (609) 698 1222. It's a family owned company and they are very knowledgable and friendly. It's made of marine grade Al and they claim it outperforms the Yanmar item. It cost $159 and they delivered it to Australia in fiver days. We will see how it goes!!

 

[nick8489]

I ***** and gripe about my elbow and manage to get about 3-4 years but I don't see the amount of corrosion you seem to have in there. Your cast aluminum elbow sound interesting although I don't know how it will stand up to hot salt water and carbon. Do you have a web site for the aluminum elbow ? Got to ask ............. in your first photo, is that a crack in the discharge or is it just the picture ?

No it's not a crack! Just the light on the Al
See my previous reply re origin of the Al elbow

 

[nick8489]

Nick: I agree that yours looks bad, but 10 years and 300 hrs is not all that bad. I am curious on how you run your engine. Do you run it at low RPM's or are you running at 2500 - 3000 when motoring? Our H'31 had several hundred hours on it and it never looked like yours. Our boat is in the California Delta so it does not have these issues like they seem to have in salt water. Our current engine is a 3JH and it has about 400 hrs on it and there are no signs of coking either.

Steve,
It's. 300 hours in two years. This is my fourth elbow ten years which I don't think is good enough.
Nick

 

[nick8489]

Nick: I agree that yours looks bad, but 10 years and 300 hrs is not all that bad. I am curious on how you run your engine. Do you run it at low RPM's or are you running at 2500 - 3000 when motoring? Our H'31 had several hundred hours on it and it never looked like yours. Our boat is in the California Delta so it does not have these issues like they seem to have in salt water. Our current engine is a 3JH and it has about 400 hrs on it and there are no signs of coking either.

Sorry Steve I forgot to answer your query about revs.
I run at 2250 rpm which according to the Yanmar fuel consumption curve is the most economical. You double fuel consumption when you get to 3000 rpm. I assume that commercial users particularly fishing folk choose this fuel consumption point.

 

[woodster]

Sorry Steve I forgot to answer your query about revs.
I run at 2250 rpm which according to the Yanmar fuel consumption curve is the most economical. You double fuel consumption when you get to 3000 rpm. I assume that commercial users particularly fishing folk choose this fuel consumption point.

i am wondering if maybe you are running a little slow.... is your top rpm 3600 if so try it at about 75 to 80 percent of the number and see if it helps slow down the carbon build up just a thought

regards

woody

 

[nick8489]

My Yanmar 4JH3E came with an extruded/welded stainless steel mixing elbow. Less radical of a bend. 500 hours on the engine I checked it last fall and it was clean as a whistle. Go figure. Maybe you can find a SS elbow for your engine?

Gunni,
The 3YM30 comes with both a SS and cast iron fitting. However on the H33 you have to fit the high rise cast version to clear the waterline.
I agree with others that SS is not the best material in this application and I understand that many have experienced cracking.
At the same time the cast iron version which Yanmar supplies seems to be too restrictive for the 3 cylinder engine (it's the same one as on the single cylinder version) Also for hot salt water and exhaust gases iron would seem the least likely material which is why I'm trying a marine grade aluminium casting. The guy making them must have discovered a market demand to have invested in a pattern and gone into production.
Interestingly the elbow connects directly to a synthetic hose so maybe there could be some composite material for a long lasting elbow.

 

[nick8489]

i am wondering if maybe you are running a little slow.... is your top rpm 3600 if so try it at about 75 to 80 percent of the number and see if it helps slow down the carbon build up just a thought

regards

woody

You may be right, but my point really is that as the premier supplier of Diesel engines for yachts they should be designed for the application. For example many yachties run their engines at low revs for long periods to charge their batteries. Can you imagine your car diesel having some sort of restriction on its rpm operation, no one would tolerate it. The components of a yacht diesel engine in the 21st century should be able to cope with running at any rpm (particularly at it's most economic level) to be considered fit for purpose. Another crazy thing about this engine is the recommendation on replacement of engine mountings. Would you design a marine diesel where the mountings wouldn't last the life of the engine?
It's interesting to see that the 2 litre VW Golf diesel is now appearing in the marine industry. My wife's Golf diesel car has done 70,000 km at all sots of revs over four years without a single component replacement.

 

[woodster]

You may be right, but my point really is that as the premier supplier of Diesel engines for yachts they should be designed for the application. For example many yachties run their engines at low revs for long periods to charge their batteries. Can you imagine your car diesel having some sort of restriction on its rpm operation, no one would tolerate it. The components of a yacht diesel engine in the 21st century should be able to cope with running at any rpm (particularly at it's most economic level) to be considered fit for purpose. Another crazy thing about this engine is the recommendation on replacement of engine mountings. Would you design a marine diesel where the mountings wouldn't last the life of the engine?
It's interesting to see that the 2 litre VW Golf diesel is now appearing in the marine industry. My wife's Golf diesel car has done 70,000 km at all sots of revs over four years without a single component replacement.

i agree with what you are saying on all accounts Nick but i have also found the concensus on the RPM's is what i have decsribed and i have always been told the that they run there best at about 75% to 80 % ...what kills me is that when i was in Victoria about 10 years ago your petrol was 1 aud per liter and at that time we were paying .90 usd per 3.8 liters here and your autos were getting a lot better mileage and i would think that had some thing to do with the epa regs here as opposed to yours not haveing all that crap on the engine we have here...not sure about how diesel compared.....and one more thought do you have a water lift muffler on your setup....if not that may contribute to the early demise of the elbows...

regards

woody

 

[John Nantz]

.... i have always been told the that they run there best at about 75% to 80 % ...

Ditto here. The Northwest Yanmar distributor for Yanmar, http://www.cascadeengine.com/ had a tech rep that came to our club and spoke about how to do maintenance on Yanmars and said the same thing. Since he was THE go-to person for the company for anything technical about Yanmar engines I would tend to believe what he says.

And it wasn't all about carbon in the mixing elbow, it is about carbon buildup in the engine cylinders, so there is more to it. He was very adamant about running in the 80% range, said the engines liked it, and at slow RPMs it causes carbon buildup.

This is a good reason to have solar panels to charge batteries instead of sitting there running the engine at idle.

 

[kloudie1]

Seems like the ells are killed by the sea water cooling.. at the lower loads, the exhaust is a lot cooler and the water cooled ell walls will condense out some nasty tars.. There is proportionally a lot more excess air in the exhaust at low loads, which can help with salt and metallic salt deposition. It takes a while for this stuff to consolidate, so if ya power up for 10 minutes or so before you shut down (increase gas velocity and temperature).. you can help make the ell last longer. You won't see this problem in land applications because the comparatively thin exhaust system runs at much higher temperatures. You can convert to a hot exhaust as was in some boats (Catalina 27 comes to mind), but having a 600+ degree pipe running through the boat is not desirable.
I agree about the engine mounts.. It seems that Yanmar could have chosen a different elastomer or design that could have preserved the elastic properties and lasted a lot longer.