Replacing Mixing Elbow

[Salty]

I am looking to replace the mixing elbow on my Yanmar 2GM20F. The elbow is all rusted out and needs to be replaced. From the look of it, I’ll have to replace both the elbow and the exhaust. I am hoping that I’ll be able to loosen the 4 bolts holding the exhaust to the heat exchanger because if I can’t, my next option is the remove everything including the heat exchanger. How difficult is it to remove the heat exchanger? Has anyone had that experience?

 

[wufibugs]

If you look through the relatively recent archives you will see that this topic was covered in great detail. I think Steve laid out the trials and tribulations of this job, and yes the easiest way is to remove the spacer still connected to the elbow, from the heat exchanger and only when both are off, separate it from the elbow. Start by soaking the bolts in Blaster overnight, tapping them, and resoaking. Steve will probably point out that this is really just a psychologically satisfying ritual, and like the rain dance, and bears absolutely no relationship to whether the bollts come lose. If nothing else, it enables us to say we tried it before we rounded the bolt heads or tore the threads out of the exchanger.

 

[Rick Sylvester]

From your teeny pictures

it's hard to tell (I'm gettin' old, dang it.) To me, it looks like the exhaust-flange area is okay. I'd take the whole mess and drop it on the parts counter of your local engine dealer and go from there. All things considered it's cheap insurance.

This is not a part you want to guess wrong on.

 

[woodster]

it is easyer to take the heatexchanger and all off and then go to a vice to take the elbow off...when you get it off rebuild the heat exchanger as well .....rod out the flues with a 22 rifle bore cleaning brush ...and bead blast the whole thing while you have it all apart ....the seals and gaskest for all of this is only about $85.00 and money well spent.....

regards

woody

 

[Ken13559]

Salty, you'll need 3 items; Mixing elbow, joint and exhaust elbow. Do note the joint has a reverse thread to mate to Mixing elbow and a normal thread to Exhaust elbow.
The upper two bolts holding the exhaust elbow to engine is short and the lower two are longer. When you have the whole assembly out, do clean up the thread/holes on the engine side. I think the joint coupling between Mixing & Exhaust elbows need not be super tight. Firmly tight and can't be moved by hands is good enough. You'll want to be able to remove them some months or a year down for cleaning/maintenance. Don't forget to replace the gasket.

 

[Alan]

Mixing Elbow

In most cases the cast exhaust elbow will not need replacement. I cleaned mine up and painted it with high temp silver paint. For sure the mixing elbow and the left/right threaded connector will have to be replaced. Use pipe dope on the threads of the connector to ensure a good seal. Don't forget to replace the gasket between the heat exchanger and the elbow.

Hint: only use a 6 point socket to remove the mounting bolts. If I recall correctly it was a 12mm socket.

 

[Steve Dion]

Alan:

It appears to me that Saltys elbow is rusted through. I would say that he will really need a new elbow.

I took mine apart on my H'31 when it was only about 5 years old and found that it had very little coking. I will tell you that we live in fresh water (but go to the sea several times a year) and from what I recall most of the sailors that have had problems live in salt water all of their life.

I would use a product like Neverseez Marine for this application.

http://www.neverseezproducts.com/marine.htm

 

[Alan]

Steve, you may be right, it's hard to tell from the picture. The casting of the exhaust elbow is much thicker than the mixing elbow and sees higher temps. My exhaust elbow is the original '93 and has spent its hole life in salt water. It was pretty rusty but a bit of wire brushing and some paint made it look new again.
I also forgot to mention to use anti seize compound on the threads of the mounting bolts. It will make all the difference in the world the next time the elbow needs to be removed.

 

[Steve Dion]

Alan:

I had not seen this Neverseez Marine before. It "appears" to be a good idea. I know that you should NEVER EVER put engine bolts together in these high temp areas without one of these products. I wish the factory would do the same.

We used a torch to very large pipe wrenches with breaker bars to seperate the elbow from the manifold. I do not think we would have ever been able to do this without the heat & the breaker bars.

Owners with gas engines should always use this stuff when replacing spark plugs. Normally this is not much of an issue, but it does help with the removal.

 

[Maine Sail]

Guys,

Please be very careful with "never-seize" products marketed as "marine". That particular never-seize product is loaded with both copper and aluminum powder. This is a recipe for galvanic issue depending upon where it is used.

For the pipe joint connections a non-hardening teflon based product like Hercules Real-Tuff or Hercules MegaLoc are perfect products. I always use both teflon tape and pipe dope together for marine wet exhaust connections.

A never-seize product with either graphite or copper or copper/aluminum powder is fine for nuts that are not subject to galvanic issues but why add more metals to the mix when TefGel is available? TefGel works wonderfully in the marine environment and won't add to the galvanic soup by throwing more metals into the mix.

For threaded pipe to pipe I would suggest a plumbers pipe dope, preferably a non hardening teflon based version like the two below.

Real-Tuff (available at Home Depot)

Tape & Dope

Megaloc (available at most plumbing supply wholesalers)

 

[Steve Dion]

MS: I don't think that this stuff is going to hold up to exhaust temps!

 

[Allan Frey]

MS, why are you against using a product with graphite? It is not a metal.

Allan

 

[Maine Sail]

MS: I don't think that this stuff is going to hold up to exhaust temps!

Tell me that when I haven't been using it for 18+ years... If your exhaust elbow gets to 550 degrees you've got other problems.. Remember 550 is the safe NSF and industry rated working range of Real-Tuff not what it can handle and still prevent leaks. That temp rating is also in conjunction with the 12,000 PSI rating of the product and your exhaust elbow is under no pressure or maybe 1 pound max. Your are only using this as a pipe thread sealer and hopefully as something that will allow them to come apart someday. Real-Tuff and Megaloc both do this quite well.

Megaloc is 400f which should still be plenty..

This is the dry side on my exhaust manifold...

 

[Maine Sail]

MS, why are you against using a product with graphite? It is not a metal.

Allan

Graphite is the most noble element in the galvanic scale everything below graphite is anodic..

http://www.corrosion-doctors.org/Definitions/galvanic-series.htm

 

[Salty]

Guys, Thanks for the suggestions. I am convince that I'll replace the whole thing (mixing exhaust, elbow and connector). I think its better to start all new. I’ll let you know how it turns out. Thanks again, really appreciate it.
　
Salty

 

[Roger Long]

I rebuilt mine a couple weeks ago. I couldn't locate the short left/right thread nipple originally used but was fortunate to have room for a higher riser which is a good idea anyway if you can fit it. The longer nipple was a "[FONT=arial,helvetica]Left/Right Nipple - 1 1/2" x 4" "Black"[/FONT] from PlumbingSupply.com. $22.97 delivered.

On advice of a couple of waterfront characters, including one who rebuilds a lot of marine exhaust systems, I used the standard grey Permatex Anti-Seize from the hardware store on the threads. I had a moment of panic when I read MainSail's posts above and then realized that it's all on the dry side so not an issue. Note that the Yanmar gasket has copper faces.

The water cooled elbow is threaded for a pipe fitting. If you were to use that, you would want to use one of the products MaineSail suggests. In my case, it's all hose and clamps downstream of the water injection.

It took a 5 foot pipe on a wrench and mega heating with a welder's torch to get the old elbow off the exhaust header flange even after weeks of soaking Sili Kroi (PB Blaster equivelant) into the threads.

There was no gasket under the flange when I took it apart but the metal surfaces were finished well enough that I never smelled a hint of exhaust in the boat.

 

[Maine Sail]

OK if we're all showing our recent exhaust elbows..

This exhaust elbow was a disaster of an installation. Who ever did this install knew nothing about thread sealants or pipe dope. It took nearly four hours of heat, PB Blaster, a massive bench vise and a 3.5 foot 1 1/4" black iron pipe as added leverage to an 18" Rigid pipe wrench to break these fittings apart. Due to the improper installation of these threaded fittings they had been leaking early on and thus rusted together as strong as I have seen in a long time. PB Blaster is great but when you are dealing with sealing threads, such as NPT, that are meant to keep fluids out, they also tend to keep most of the PB Blaster out too.
This exhaust flange fitting is a $90.00 part from Universal so I clearly wanted to save it for the owner.

So after many hours and a very long pipe on the end of a very robust pipe wrench the nipple finally gave up its hold. The force needed to remove it from the exhaust flange crushed and made it oval.

This is what my 3.5 foot black iron pipe looked like after I broke the stuck fittings free. I have not done the calculation on how much force I applied but all my 200+ pounds were going into that leverage pipe and the fitting was over 4.5 feet away away from the end of the pipe.

As I mentioned this entire project was a comedy of errors. Either the previous owner who did all this work was a really bad DIY guy or he hired the worst mechanics on the planet. There was no reason for this exhaust elbow to be tilted off center other than the fact that the installer refused to use pipe dope or thread sealant to mate the NPT fittings together.

It probably bound up and refused to turn anymore so they just left it tilted off center. Due to this laziness, or lack of understanding, it caused the exhaust elbow to chafe, vibrate, dent and make a career ending thin spot in the heat exchanger. Cha-ching $$$$ more unnecessary expense for the boat owner $$$$.

This manifold will fit and will clear the bulkhead & heat exchanger when installed correctly, it was not.

 

[Salty]

Surprise! Surprise! The 4 bolts holding the mixing exhaust to the heat exchanger came off easily with little resistance and I was able to get the mixing exhaust and elbow out. Now I did some online searching and couldn't find any suppliers. Does anyone know of an online supplier for the Yanmar 2GM20F mixing elbow and exhaust? I was also thinking of changing out the 4 bolts to studs. Is that a good idea?

Thanks
Salty

 

[Roger Long]

Does anyone know of an online supplier for the Yanmar 2GM20F mixing elbow and exhaust?

[url]http://shop.torresen.com/marine_diesel_direct/Yanmar/
[/URL]

 

[seadaddler]

Port Jeff

I don't remember the name but a when living on LI some time around 2005 I got yanmar parts from a supplier in Port Jeff.
Try the Old man marina or some like that name might be able to help or the Mt Siani sailing Club might be able to help with the supplier in Port Jeff.
Nick