Please advise what is the size (diameter and thread) of a mixing elbow main upper threaded connection to exhaust manifold flange? Is it NPT, or BSP, or metric?
Thank you,
Michael.
Thank you,
Michael.
Yanmar 2QM20 mixing elbow
- Thread starter misha93
- Start date
Various combos of 'nozzles' in the exhaust system are used on the QM series engines, depending on how low the engine is mounted in relation to the static waterline of the boat to the engine in the boat.
The 'OEM' is a totally flanged (to the exhaust manifold) with a 1.5" (40mm) ID to hose connection.
The 'most common' for 'dry stack' arrangements for QMs are: a 4 bolt flanged connection to the ex. manifold with internal threads to accept 1-1/2 black iron NPT threaded PIPE for the 'riser' --- and the (usually of after-market origin or Westerbeake) mixing elbow is connected to the top of 'black iron' 1.5" NPT threaded pipe.
With so many possible variables, youre going to have to disassemble and measure.
The 'OEM' is a totally flanged (to the exhaust manifold) with a 1.5" (40mm) ID to hose connection.
The 'most common' for 'dry stack' arrangements for QMs are: a 4 bolt flanged connection to the ex. manifold with internal threads to accept 1-1/2 black iron NPT threaded PIPE for the 'riser' --- and the (usually of after-market origin or Westerbeake) mixing elbow is connected to the top of 'black iron' 1.5" NPT threaded pipe.
With so many possible variables, youre going to have to disassemble and measure.
Some pictures
For what it's worth the attached show the flanges, the new mixing elbow in the flange and the old mixing elbow. Due to corrosion I had the flange faces skimmed.
The good new is, mixing elbows are not very expensive.
For what it's worth the attached show the flanges, the new mixing elbow in the flange and the old mixing elbow. Due to corrosion I had the flange faces skimmed.
The good new is, mixing elbows are not very expensive.
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Gentlemen,
Thank you very much for the prompt replies. The cost of the original cast steel mixing elbow varies from $200 to $600. If Yanmar uses NPT it would be easy to make up an assembly using standard SS threaded pipe fittings for a fraction of cost. My elbow after 3 years in sea waters was reduced to dust, I just hope that the flange is in a better shape and may be reused. I am going to check this out this coming weekend. If my project becomes a success, I would be glad to share it in this forum.
Thank you very much for the prompt replies. The cost of the original cast steel mixing elbow varies from $200 to $600. If Yanmar uses NPT it would be easy to make up an assembly using standard SS threaded pipe fittings for a fraction of cost. My elbow after 3 years in sea waters was reduced to dust, I just hope that the flange is in a better shape and may be reused. I am going to check this out this coming weekend. If my project becomes a success, I would be glad to share it in this forum.
If my memory is correct, the new mixing elbow in the picture was $85 in 2008. The exhaust manifold would have been $600. Did you get actual quotes? If so I would be very interested in your project because it has been 5 years in sea water.......
When I replaced my 2QM20 mixing elbow several years ago (it was they type shown in JohnB's photo of this thread), I took the thread flange piece down to the local hardware store just to see about the thread size -- with same idea as you that maybe one could be fabricated from SS piping. Or if fabrication was cheap enough, maybe even standard SS pipe could be used -- just replace more frequently.
Standard plumbing pipe did thread in fine.
Eventually I found a Yanmar official replacement elbow a that a local chandlery had let languish in inventory for quite a few years and they were still carrying it at their original acquisition price. I paid $135 for it, but everyone else was giving me a price of just north of $200.
Standard plumbing pipe did thread in fine.
Eventually I found a Yanmar official replacement elbow a that a local chandlery had let languish in inventory for quite a few years and they were still carrying it at their original acquisition price. I paid $135 for it, but everyone else was giving me a price of just north of $200.
Hi Misha93)
Yes, let us know. Particularly how you would integrate the cooling water feed into the actual steel part of the elbow to a) keep the steel cool and b) not have a tendency to back up into the manifold!
For what it is worth, the flange on my 2QM20 was in fine shape when I removed to replace the elbow. But also the engine since 1980 was anti-freeze cooled. It was necessary to bring the flange home with the elbow still attached to break the two apart on my large vice. I sure was nervous about cracking the flange in the process, but it eventually broke free without damage. Be sure to use lots of anti-seize paste when you reassemble.
One of the pieces would be a standard 45Deg. 1-1/2" elbow, next to it is reducing tee, 1-1/2"x1/2'x1-1/2" and then 1-1/2" pipe nipple threaded one end. The other not threaded end is for a hose. Into 1/2' tee connection is for a barbed adapter to attach hose of cooling water. I am not sure about sizes, I need to have the original elbow in hand in order to do a proper design.
integrate the cooling water feed into the actual steel part
Dear fellow sailors,
Finally I’ve got all info and parts to build the mentioned before “homemade” mixing elbow using standard pipe/tube fittings. The vendors are: McMaster-Carr and Swagelok. The bill of material is as follows:
1. Multipurpose 304 SS Tube 0.049” wall thk.3/4”OD McMaster-Carr p/n 1750T113 $35.29
2. Low pressure galvanized iron threaded Tee 1-1/2” NPT female-female-mail connections. McMaster-Carr p/n 4638K373 $36.59
3. Low pressure galvanized iron threaded 45 deg. Elbow 1-1/2” NPT female-mail connections. McMaster-Carr p/n 9110&77. $17.99
4. Standard wall 316 SS threaded one end Nipple 1-1/2” NPT 6” length McMaster-Carr p/n 4638K373 $18.77
5. 316 SS Reducing Bushing 1-1/2” Male NPT X ¾” female NPT McMaster-Carr p/n 4452K187 $36.59
6. SS Bored Through Male connector ¾”OD Swagelok p/n SS-1210-1-12BT $29.48
7. SS Union Elbow ¾” OD $58.34.
The material selection was defined as you may see from the bill of materials were galvanized iron for the pars with no contact with sea water and exposed to exhaust gases and stainless steel for the wetted parts exposed to cooling sea water. This was mostly done for an economy purpose.
Please see the old mixing elbow and the new assembly in the pictures. The new assembly is slightly more bulky than the original one but it fits in an available space in the engine room. There was a challenge to insert the union elbow (item 7) with two swaged tubes into the tee (item 2) due to the narrow space. The tubes to be tightened already inserted using a narrow 1-1/8” size wrench.
So for the total of less than $130 I want to believe that this will last long.
I would be happy answering any questions.
Yes, let us know. Particularly how you would integrate the cooling water feed into the actual steel part of the elbow to a) keep the steel cool and b) not have a tendency to back up into the manifold!
For what it is worth, the flange on my 2QM20 was in fine shape when I removed to replace the elbow. But also the engine since 1980 was anti-freeze cooled. It was necessary to bring the flange home with the elbow still attached to break the two apart on my large vice. I sure was nervous about cracking the flange in the process, but it eventually broke free without damage. Be sure to use lots of anti-seize paste when you reassemble.[/QUOTE]
Dear fellow sailors,
Finally I’ve got all info and parts to build the mentioned before “homemade” mixing elbow using standard pipe/tube fittings. The vendors are: McMaster-Carr and Swagelok. The bill of material is as follows:
1. Multipurpose 304 SS Tube 0.049” wall thk.3/4”OD McMaster-Carr p/n 1750T113 $35.29
2. Low pressure galvanized iron threaded Tee 1-1/2” NPT female-female-mail connections. McMaster-Carr p/n 4638K373 $36.59
3. Low pressure galvanized iron threaded 45 deg. Elbow 1-1/2” NPT female-mail connections. McMaster-Carr p/n 9110&77. $17.99
4. Standard wall 316 SS threaded one end Nipple 1-1/2” NPT 6” length McMaster-Carr p/n 4638K373 $18.77
5. 316 SS Reducing Bushing 1-1/2” Male NPT X ¾” female NPT McMaster-Carr p/n 4452K187 $36.59
6. SS Bored Through Male connector ¾”OD Swagelok p/n SS-1210-1-12BT $29.48
7. SS Union Elbow ¾” OD $58.34.
The material selection was defined as you may see from the bill of materials were galvanized iron for the pars with no contact with sea water and exposed to exhaust gases and stainless steel for the wetted parts exposed to cooling sea water. This was mostly done for an economy purpose.
Please see the old mixing elbow and the new assembly in the pictures. The new assembly is slightly more bulky than the original one but it fits in an available space in the engine room. There was a challenge to insert the union elbow (item 7) with two swaged tubes into the tee (item 2) due to the narrow space. The tubes to be tightened already inserted using a narrow 1-1/8” size wrench.
So for the total of less than $130 I want to believe that this will last long.
I would be happy answering any questions.
Yes, let us know. Particularly how you would integrate the cooling water feed into the actual steel part of the elbow to a) keep the steel cool and b) not have a tendency to back up into the manifold!
For what it is worth, the flange on my 2QM20 was in fine shape when I removed to replace the elbow. But also the engine since 1980 was anti-freeze cooled. It was necessary to bring the flange home with the elbow still attached to break the two apart on my large vice. I sure was nervous about cracking the flange in the process, but it eventually broke free without damage. Be sure to use lots of anti-seize paste when you reassemble.[/QUOTE]
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Misha93:
Thank you so much for following up with your promise of posting your mixing elbow solution. Certainly a well thought-out creative use of parts and the combination of the SS and galvanized piping is great. I will study your parts list and description more over the next several days and ask questions I am sure.
Have you installed it on your engine yet and gone motoring? (OK I see that you are located in MA ... so probably hauled out for winter now!?) One of the aspects of the Yanmar original elbow (the one in your picture with the hole in it), I think is that the raw water interfaces a large amount of surface area within the elbow which I would think keeps the metal cool. Your solution very nicely directs the raw water down the exhaust tube as a safeguard to prevent the water from entering the engine. Will be interesting to verify if its enough to prevent the elbow from becoming too hot.
Again great stuff! Thanks.
Thank you so much for following up with your promise of posting your mixing elbow solution. Certainly a well thought-out creative use of parts and the combination of the SS and galvanized piping is great. I will study your parts list and description more over the next several days and ask questions I am sure.
Have you installed it on your engine yet and gone motoring? (OK I see that you are located in MA ... so probably hauled out for winter now!?) One of the aspects of the Yanmar original elbow (the one in your picture with the hole in it), I think is that the raw water interfaces a large amount of surface area within the elbow which I would think keeps the metal cool. Your solution very nicely directs the raw water down the exhaust tube as a safeguard to prevent the water from entering the engine. Will be interesting to verify if its enough to prevent the elbow from becoming too hot.
Again great stuff! Thanks.
Installation was completed yesterday Nov. 16. It looks as it is in this picture. Three fittings at the bottom were added to line up with hose.
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Mine needs replacing, and the quote I got from the machine shop was $300. That was in black iron, since apparently SS doesn't hold up. That seems a bit high to me, anyone got any good links to a cheaper place?
Check this place out: www.exhaustelbow.com. I bought a SS elbow for my Yanmar 1GM and was very happy with the price and the service.
Thanks - I've emailed him to see if that mixing elbow is compatible with my engine. I'm also looking at the method posted earlier in the thread, but being in Canada I don't have access to McMaster-Carr, and the parts are about $100 more expensive.