Yanmar Exhaist elbow

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Spyro

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This is a pic of the elbow on my 2GM20. I know it was replaced a few years before I bought the boat. Today is the first time that I have noticed it doesn't look right. I think the elbow fitted is for a 1GM10 as it only has 3 bolts holding it in place. There is a hole for a 4th bolt which maks me suspect it's the wrong elbow that's been fittted. Does anyone else with the engine have a set up like this. I was going to take the elbow off to have a look for corrosion. From what I can tell from this site http://www.exhaustelbow.com/ the 2gm20 has larger inlets and outlets. If it is the wrong one should I replace it?

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2gm20 raw water cooled is a 3 hole elbow, if you have a 2gm20F - freshwater cooled unit - then it's a 4 hole elbow.

http://www.marine-power.co.uk/index.php?route=product/product&path=20_83&product_id=231

http://www.marine-power.co.uk/index.php?route=product/product&path=20_83&product_id=233

If you do replace it, remember on refit you will need a new gasket, it is extremely unlikely the old one will be fit to be reused. I have found they rip apart when the elbow is removed.

PS links for info, I note your reference to exhaust elbow company
 
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Spyro said:
This is a pic of the elbow on my 2GM20. I know it was replaced a few years before I bought the boat. Today is the first time that I have noticed it doesn't look right. I think the elbow fitted is for a 1GM10 as it only has 3 bolts holding it in place. There is a hole for a 4th bolt which maks me suspect it's the wrong elbow that's been fittted. Does anyone else with the engine have a set up like this. I was going to take the elbow off to have a look for corrosion. From what I can tell from this site http://www.exhaustelbow.com/ the 2gm20 has larger inlets and outlets. If it is the wrong one should I replace it?

WP_20141214_003_zps4f0833a5.jpg
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Do you suspect it's not working correctly? Otherwise I would put off doing anything different until it fails, or you need to make a substantial hole in your wallet.!
 
pagoda said:
Do you suspect it's not working correctly? Otherwise I would put off doing anything different until it fails, or you need to make a substantial hole in your wallet.!
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Yes, but --- the elbow should be checked regularly to make sure that it is not clogged up with carbon etc. Also holes in the inner tube are impossible to see without removal and cleaning out? The result of internal failure can be water in the cylinders which can be a bit serious!! First time I removed mine it looked fine but on cleaning out and closer inspection, the inner tube was riddled with holes.

Obviously frequency will depend on how much you use the engine but I check mine about every two years and I carry a spare on board in case it needs replaced plus a few gaskets so I can refit if it is OK?
 
pagoda said:
Do you suspect it's not working correctly? Otherwise I would put off doing anything different until it fails, or you need to make a substantial hole in your wallet.!
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Graeme
No problem with it but I know these are prone to failing and causing bigger problems. The previous owner had to get a new cylinder head after the first one failed. It was around 8 or 9 years ago it was replaced. It looks great from the outside but as said in the last post I thought it would be worth checking and that's why I was having a look today.
I've since received this reply from The exhaust elbow company in my first link. So it looks like it is ashould be.

"Hi Ian, some of the 2GM's do share elbows with the 1GM so that appears to be the correct one for your motor. The fourth bolt hole is there for use the high-rise mixing setup sometimes installed when the exhaust is below the waterline. Great picture there, thanks for the interest. Best, Ben"
 
You really should check it annually. My elbow looked great from the outside and I assumed it was OK. Then, after reading something about the elbows in PBO a couple of years or so ago, I removed mine, only to find the inner tube had perforated. It's only a few minutes' work to take it off, and even if you have to replace the gasket, it's much less costly than £600 for a new cylinder head.

I had a new stainless tube welded into my elbow for less than £60. Checked it this Autumn and all's well.
 
Spyro said:
Is the gasket just paper?
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No, it's a fairly thick heat resistant metallic sort of thing. Not sure what it's made of but definately not paper. Problem is that when tightening up the elbow, the gasket deforms to match any irregularities in the opposing surfaces. It usually rips apart when the elbow is removed. I have always had to take sharp edge - chisel etc - to the surfaces to clean the residue off.

Here's the one for the 3 hole Yanmar

http://www.marine-power.co.uk/index.php?route=product/product&path=20_83&product_id=232
 
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Neil at west coast Marine at Troon seems to be clued up on Yanmar bits. The slightly fibrous metal clad gaskets DO fall to bits if you disturb them...
My exhaust elbow is not quite standard, apparently not many of that style were made, however Neil tracked it down for me. (3GM30 raw). I took the head off last year to clean up the waterways, needed quite a few gaskets by the time it was all back together!

Graeme
 
Pardon my ignorance but can I inspect the elbow in situ by removing the hose and thereby not needed the gasket?
Thanks
Martin
 
Halo said:
Pardon my ignorance but can I inspect the elbow in situ by removing the hose and thereby not needed the gasket?
Thanks
Martin
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Not really. The Yanmar design is 2 concentric, curved tubes, welded at the mounting flange. The usual, and potentially most damaging failure is near the weld, out of direct vision.
A borescope might help, but simpler to remove the elbow I'd think.
You can cut a gasket out of compressed fibrous sheet jointing, (asbestos or CAF, no longer allowed), but it's a bit of a hassle.
 
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Halo said:
Pardon my ignorance but can I inspect the elbow in situ by removing the hose and thereby not needed the gasket?
Thanks
Martin
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3GM30F. When I had the exhaust hose off at the beginning of the season I inspected the elbow as well as I could, poking my finger up the gas side and trying to use a mirror to see the water side. All appeared to be well. Within a few weeks there were signs that water was leaking from the weld at the bottom, where the water jacket meets the mounting flange. Not complaining, it is 10 years old, just confirming that it is not easy to inspect. Although I'm not sure I could have seen the internal failed area with the manifold in my hand.
 
The easiest way to check when it is off is to turn it upside down, block off the injection spigot and fill the gap between the tubes with water, If there are holes in the inner tube then water leaks out through the exhaust pipe.
 
Tranona said:
The easiest way to check when it is off is to turn it upside down, block off the injection spigot and fill the gap between the tubes with water, If there are holes in the inner tube then water leaks out through the exhaust pipe.
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Although sometimes the holes can be obscured by carbon build up in the tube and only become obvious when the inner tube has been "decoked"
 
lydiamight said:
If your exhaust elbow needs replacing why not replace it with a stainless steel one? Much cheaper than the Yanmar original equipment.

See here http://www.exhaustelbow.com/
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My original Yanmar manifold is made in a 300 series stainless steel. I'm not sure about his choice of 304 stainless (A2), I would have thought 316L would be far better.
 
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