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Yanmar Exhaust Elbow / cheap, quick fix.

Jul 15, 2014
73
Oday 322 Freeport, Bahamas
I noticed black smoke when I increased the throttle (engine bogs). It was obvious that the exhaust elbow had carboned up - this elbow is truly an atrocious design. Since I've seen this on several Yanmar's I've owned, I thought I'd pass along a cheap, quick and long term fix.
It takes less than 15 minutes to remove the exhaust manifold with the elbow. Just undo the 4 bolts holding the manifold to the engine.
Put it in a vice (or between 2 logs like I did) and remove the exhaust elbow and the short stainless joiner piece. Go to any plumbing store (or Home Depot) and buy (Schedule 40) 1 1/2 inch NPT (national pipe thread) a 3 inch nipple, a 90 elbow, a 2 inch nipple, a 90 elbow, a 6 inch pipe threaded at at least one end.
About 4 inches down on that 6 inch piece, drill and tap a 1/2 inch nipple (for the water injection).
Into the exhaust manifold, screw in the 3 inch nipple, then the 90, then the 2 inch nipple, then a 90 and then the 6 inch section. Now you have a new exhaust elbow for under $30-.
I go to a motorcycle shop and get some exhaust wrap for the heat but I have gone months without that.
My engine has 1392 hours (hour meter was installed a year after boat was launched so maybe 50hrs more) and previous owners have replaced that Yanmar elbow at least twice at over $400-each.
 
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Jul 15, 2014
73
Oday 322 Freeport, Bahamas
I am up north for a week but will take pictures next weekend. I got the idea from this post
https://svsmitty.wordpress.com/2013/04/29/custom-exhaust-risermixing-elbow/ I simplified his design (his water injection was too complicated for me). I reused the bronze nipple from the old yanmar elbow for the water injection (to cool the exhaust system). I drilled and tapped (about 2 inches from the end of the pipe) into the lower portion of the 6 inch section of pipe and ran the water to that.
I used 1.5 inch Schedule 40 Black Pipe - common and easily available. Just imagine an upside down U - made from 3 pipe pieces and two 90 degree elbows.
Total time (including R&R) from start to finish was less than an hour BUT the Oday 322 has easy engine access.
 
Jul 15, 2014
73
Oday 322 Freeport, Bahamas
Better than a picture:
Here is a drawing, parts list and instructions.
Exhaust system full of carbon is one of the most common problems with diesel engines. I have seen people pull their injection systems for no reason. If you experience LOTS of black smoke, a "boggy" engine, no high end RPM's - check your exhaust system.
AGAIN - the DISCLAIMER:
This is not an original Yanmar engineered or approved part. It's just a DIY fix put together from internet searches.
I have used it and it works.
SPACE ISSUES:
The 2 inch nipple in position #4 on the sketch can be a 1 inch or 1.5 in nipple
 

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Last edited:
Jan 7, 2011
2,751
Oday 322 East Chicago, IN
I am not sure that arrangement would fit in my O’Day 322 engine compartment...my elbow is already pressed up against the frame for the engine box.

Did you have some clearance between the original elbow and the engine box?

Greg
 
Jul 15, 2014
73
Oday 322 Freeport, Bahamas
It is no wider (you can also say it's no longer) than the original Yanmar Exhaust Elbow. The drawing shows more space between the the two vertical sections of pipe than there really is. It's also important to remember that the water injection nipple is not where I show it in the sketch. It needs to be moved 90 degrees so it comes out the back side of the 6 inch pipe. That way the original water hose can be reused. I drilled and tapped for that nipple and put a bit of quick dry (24 hr) 5200 on the threads. I know 5200 is the Devils Glue but it's good for up to 250F and since water goes through this nipple, temp isn't an issue.
I know it fits a 322 but if your engine box is in any way different from mine (Hull Number 35) then it's no problem to use a 1- or 1.5 inch nipple instead of a 2 inch nipple in Sketch position #4
This is an easy job.
 
May 17, 2004
3,369
Beneteau Oceanis 37 LE Havre de Grace
The drawing attachment contains a virus. Do not try to open it.
Virustotal.com, which scans uploaded files with 57 different antivirus tools, says it's completely clean. You may have a latent virus on your system which caused the alert, or it may have just come up coincidentally from another browser tab.
 
Jul 15, 2014
73
Oday 322 Freeport, Bahamas
#1 the sketch I did (as you can see) by hand today. The typed words were printed on a second piece of paper and glued onto the paper with the sketch. No computer was used to generate the original document.
It was then scanned on a new Cannon scanner where it was saved as a pdf on a 3 month old Dell laptop. I have never had a facebook, twitter, spotify or what's app account (where most viruses get passed) and Windows Defender did a full scan yesterday. I just ran malwarebytes and can find no virus in my system.
It should also be noted that many free virus scanners report an "issue" so you'll buy the premium version.
Gary
 
Aug 5, 2016
25
Catalina Capri 22 Cambridge
The best part is that it is fail safe. The Yanmar elbow has the potential of flooding the engine exhaust if the elbow fails catastrophically internally.
 
Jul 15, 2014
73
Oday 322 Freeport, Bahamas
Back in The Bahamas - a week up north is a bit much in the winter.
I was going to take pictures of my DIY exhaust manifold but all you could see was the heat wrap.
Luckily, an Express 35 limped in and needed a new exhaust elbow, his was rusty as well as plugged with carbon. He couldn't find and black pipe on the island so have to make do with plain old galvanized 1.5in pipe.
I have attached three almost identical pictures just from different angles. He broke his bronze water injection nipple off while trying to remove it. I tasked him to buy a 3/8 pipe nipple but 1/2in was all he could find. We're searching for a 1/2in tap so the nipple isn't fitted yet but it is shown in the pictures.
If you have a space issue, the 2 inch nipple between the two 90 degree elbows can be reduced to a 1 inch nipple instead.
The dark part is the original Yanmar exhaust manifold in the picture. I am not a metallurgist but think plain galvanized pipe is a short term fix and that it needs to be at least Schedule 40 Black Pipe. But down here, beggars can't be choosers.
 

Attachments

Jun 11, 2004
1,185
Oday 31 Redondo Beach
Better than a picture:
Here is a drawing, parts list and instructions.
Exhaust system full of carbon is one of the most common problems with diesel engines. I have seen people pull their injection systems for no reason. If you experience LOTS of black smoke, a "boggy" engine, no high end RPM's - check your exhaust system.
AGAIN - the DISCLAIMER:
This is not an original Yanmar engineered or approved part. It's just a DIY fix put together from internet searches.
I have used it and it works.
SPACE ISSUES:
The 2 inch nipple in position #4 on the sketch can be a 1 inch or 1.5 in nipple
You mentioned galvanized pipe gassing off over the first few hours. My understanding is that black iron pipe is preferred to galvanized for DIY exhaust projects.
 
Jul 15, 2014
73
Oday 322 Freeport, Bahamas
My "how to" states to use Schedule 40 Black Pipe however in Abaco, we couldn't get Black Pipe so used plain galvanized pipe. It gasses off for a while (not exhaust gas).
The owner of the Express 35 that we just made the exhaust elbow for knows that when he gets back to Florida in May he has to redo with black pipe.
We hunted down a 3/8 bronze fitting to use for water injection this afternoon so all good.
 
Jun 19, 2004
360
Morgan M28 O/I Ocean Gate, NJ
You might be interested in the small diesel exhaust riser by Barr Marine. Available in cast iron and aluminum. It has 1-1/2" inlet and outlets. Check their catalog; p/n 20_0094. Our M3-20 has this elbow with a couple of standard pipe couplings. Nice piece and low cost too...
 
Dec 16, 2020
1
Spencer Spencer 31 Gibsons
You might be interested in the small diesel exhaust riser by Barr Marine. Available in cast iron and aluminum. It has 1-1/2" inlet and outlets. Check their catalog; p/n 20_0094. Our M3-20 has this elbow with a couple of standard pipe couplings. Nice piece and low cost too...

Hi from Mark in BC Canada. I am posting a meesage to you in responce to the post you made above on February 3, 2018. I have a Spencer 31 sailboat that is new to me. The PO had made his own exhaust mixer elbow that I am concerned is an accident waiting to happen. The engine on this boat is a Kubota DH850-B. The setup seems to be the same as a Universal M25. The engine has a Barr wet manifold and I purchased the Barr riser that you noted. I purchased the Barr riser before seeing your post. After buying the Riser I was concerned about the weight (10Lbs) hanging off of the manifold. It seems the bolts holding the manifold on are not very large in diameter. As well I have read about the concerns over this type of riser that injects the cooling water in the back of the riser due to the posibility of a hole developing due to corrosion that would allow water to enter the engine. Is there anything you could share with me regarding your experience with this riser? In particular did you do anything to help support the weight such as a bracket attached to the bell housing? Thank you.