yanmar exhaust elbow. beware!

NPMR said:
this is a problem that is so, so common to Yanmar engines (my 1GM10 had it and now my 3YM20) that I cannot understand why Yanmar don't fix or redesign it? The designs are 20 years or so old or more and they STILL have not sorted it. How many engines have been damaged or even ruined by this awful piece of junk?
Click to expand...

If Yanmar refuse to fix the problem then maybe the replacement market is calling for a better design. If a successful design is available then there may even be a market to owners of newly installed engines who don't want to risk their new pride and joy.
 
If they need to removed and checked every year then it follows that many may have to be replaced every year.

This makes them a consumable item like a fuel or oil filter. So where are the OEM replacements. They ought to be as common as filters surely.
 
NPMR said:
Two things occur to me;

1) this is a problem that is so, so common to Yanmar engines (my 1GM10 had it and now my 3YM20) that I cannot understand why Yanmar don't fix or redesign it? The designs are 20 years or so old or more and they STILL have not sorted it. How many engines have been damaged or even ruined by this awful piece of junk?

2) The warnings to check the exhaust are nowhere near visible enough. Apparently my local Yanmar dealer suggests EVERY year but where does it tell the luckless owner to do this? Certainly not the boat builder and I haven't found it in the user manual - happy to be corrected if it is there, but if it is, why not highlighted as it is a huge potential safety problem if your engine breaks at a crucial moment.
Click to expand...

User manual actually states as part of the 1000hr serveice on the 3YM that the exhaust elbow is taken off and cleaned.

I still haven't done mine @ 2100 hrs - it does have some corrosion weep from the weld of flange to pipe.
Now I've got a spare I might do the job.
I'd not accept that the water-damaged 2GM20 was down to the exhaust mixer, but rather to the well-known problem that all raw water cooled GM models suffered coolant leaks past the head gasket.
 
Last edited:
charles_reed said:
User manual actually states as part of the 1000hr serveice on the 3YM that the exhaust elbow is taken off and cleaned.

I still haven't done mine @ 2100 hrs - it does have some corrosion weep from the weld of flange to pipe.
Now I've got a spare I might do the job.
Click to expand...

Mine is almost exactly the same, 2200 hours on a 3GM30F. I detected some water leakage from the same weld last season and bought a replacement. It didn't seem to get any worse through the year but I will replace it at the beginning of this season. Incidentally, the genuine Yanmar manifold was considerably cheaper bought in the Agmar chandlery in Leros than it would have been in UK.
 
KevO said:
Ben says they are currently 304 with 308L welds. He has been directed to these threads and says he will consider changing to 304L for future products :)
Click to expand...

The 'L' grades have slightly better corrosion resistance than the higher carbon ones. However, their main benefit is in reducing sensitisation. This is the reduction in chromium content adjacent to the weld, caused when it diffuses away to form chromium carbides. The metal at the weld is then susceptible to increased corrosion. This is normally reckoned to occur only in sections greater than 6 mm, as the heat declines too rapidly for the diffusion to take place in thinner ones. However, I have seen it many times in sections a lot less than 6 mm, e.g. flare stacks offshore, only about 4 mm. It follows that a manifold with a pipe wall thickness of 3-4 mm welded to a flange of 5-6 mm might well be at risk.
 
Just taken the elbow off my 3YM30. A clean up around inside the gas inlet end has revealed a ring of pits about 10mm in. Looks like a new one needed. The engine is a 2005 with 1100 hours and has already had one replacement elbow. Looks like a p*ss poor design. At least I have caught it before serious engine damage.
Martin
 
Just to add to your gloom on the matter of these stupid exhaust elbows -- In the USA, the $ charge is about the same as the UK £ price - so the cost in the US is only a little over half what it is over here!!!!! And Yanmar won't let the US dealers export to the UK as part of their terms of business!! Barrus, the UK importer feel that they are not overcharging us. I wonder why?

Good Innit?

PS Going to USA soon - remind self to bring one back with me
 
On my 3GM30F, the issue was that the exhaust elbow was full of crud where a miniscule amount of water was passing through - the effect was that the engine wouldnt go past c. 1800 revs. Change the elbow and problem has gone away. I will remove the elbow annually to check for any build up of crud.
 
20140430_201223_resized.jpg
Replaced my 2GM20F exhaust elbow late last season after it began blowing slightly. It came off without any difficulty and then when I examined it on the bench to separate the stainless nut it fell apart in my hands. Replaced with original part as not alternative options available ! There must be an engineer somewhere who can produce a SS alternative ?
 
alahol2 said:
If Yanmar refuse to fix the problem then maybe the replacement market is calling for a better design. If a successful design is available then there may even be a market to owners of newly installed engines who don't want to risk their new pride and joy.
Click to expand...

Or mention when buying the engine from the dealer that there will be no purchase unless elbow is sorted. But who knows of this problem when buying in the first place. The old HM series never suffered from this, so its a manufacturing cutback.
 
Worried about mine now, but I wanted to get a new gasket before taking it off. So down at the boat I found that the manifold flange has four bolt holes, but only three bolts are fitted. I thought raw cooled engines used a three-bolt flange, so has someone fitted a freshwater cooled manifold on mine, or would the three holes not line up?
 
You must log in or register to reply here.

Share this page

Top