exhaust elbow issues on 1gm10. Why don't they make them in bronze?

[niallw70]

My existing exhaust elbow had multiple little holes in the inner sleeve due to corrosion. Its also caused me corrosion problem in the head and also a seized valve. I've tried to patch up the elbow with some plumbers flue silicone sealant, squishing the sealant into the holes with my fingers from both ends. This should work as a temporary bodge to get me to end of the season, but I think I do need to buy a replacement.
It occurred to me stainless steel is the wrong material for the job. Why don't they make these things in bronze? Oh ofcourse I think I already know, replacement SS exhaust elbows for their GM series engines must be a useful source of revenue for Yanmar.
Bronze would be more expensive material for elbow but much more likely to last the lifetime of typical engine, saving thousands in the long run.
With an gm engine operating temp between 60-70degC even plastic could be a choice.

 

[jamie N]

I've had 2 SS elbows made for individual engines by a local welder here. They cost very little and have never given a problem over many hundreds of hours.
I removed the old item, dropped it at the welder and picked the new one up when told; easy peasy!
I absolutely agree with you, and feel that it's verging on an incompetent design to have 'mild steel & heated sea-water' together.

 

[Tranona]

Never seen an exhaust elbow made of bronze. Most common are cast iron and stainless. The problem with the standard Yanmar one is the grade of stainless used and to an extent the quality of the welding of the inner to the outer. Aftermarket replacements such as this Yanmar 1GM, 1GM10 Exhaust Elbow Kit are made of 316 and seem to last much better.

 

[vyv_cox]

The failure mode of the Yanmar stainless steel elbows that I have seen, including my own, is thermal fatigue. The disparities in thickness between flange, inner and outer tubes lead to high stress at the welds as one component expands but is restrained by another. After 2500 hours mine was severely cracked but barely corroded at all. Photos and text here Fatigue

 

[Tranona]

The 1GM is rather different as the OP has found. While the weld can fail the most common cause of failure is perforation of the inner sleeve, caused I believe by a combination of the spray pattern from the injection point and the habit of the engine running backwards for a couple of revs when shutting down. This seems to suck seawater back up the pipe that causes the damage to the head and valves.

Best way of checking is to remove the elbow from time to time, invert it, block the injection point and fill the gap between the inner and outer with water. This will show up any little holes in the inner pipe which cannot be seen from visual inspection.

 

[Spirit (of Glenans)]

The Volvo D-series engines come from the factory fitted with cast-iron elbows which eventually fail due to corrosion and the common advice on here is to replace them with a stainless steel aftermarket version.

 

[bignick]

You can buy stainless replacements for these. There was a write-up in PBO a few years ago.

 

[Plum]

My existing exhaust elbow had multiple little holes in the inner sleeve due to corrosion. Its also caused me corrosion problem in the head and also a seized valve. I've tried to patch up the elbow with some plumbers flue silicone sealant, squishing the sealant into the holes with my fingers from both ends. This should work as a temporary bodge to get me to end of the season, but I think I do need to buy a replacement.
It occurred to me stainless steel is the wrong material for the job. Why don't they make these things in bronze? Oh ofcourse I think I already know, replacement SS exhaust elbows for their GM series engines must be a useful source of revenue for Yanmar.
Bronze would be more expensive material for elbow but much more likely to last the lifetime of typical engine, saving thousands in the long run.
With an gm engine operating temp between 60-70degC even plastic could be a choice.

Bronze works well! I ordered a new exhaust injection bend from Vetus as the original cast iron one was falling appart after 13 years. I was surprised to find the replacement from Vetus was cast bronze, exactly the same design. This year I removed it for inspection while working on the heat exchanger and after 18 years it was excellent on the inside! No dezincing at all so it is obviously not brass. Hopefully good for another 18 years!

Www.solocoastalsailing.co.uk

 

[Neeves]

I really don't think the elbows are big issue for the engine suppliers. The engines are not sold to 'us' but to the large yacht builders. Its no good us complaining to the engine supplier - we simply do not come into the equation. I also suspect that we actually don't come into the equation for the yacht builders either - as all the engines have the same issue, so we cannot demand a different engine and individually we don't really count (in the same way the charter fleets might count).

Adding to the weakness of our position - most new yachts are serviced by cheque book - many owners will not know how to spell 'exhaust elbow' and certainly will not know what it means

We demand our, individual, independence - that's part of the beauty of sailing - the downside is we do not have a powerful voice.

I'm as much at fault - I just grin and bear it, and get my cheque book out for a new one. Who do I complain to - the purveyor of elbows is the local service agent, who relies on replacing elbows as part of his income.


I'm just off to weep in the corner!

Jonathan

 

[lustyd]

The engines are not sold to 'us'

Realistically though, how many people buying a new yacht ever actually get to the stage where this affects them? I agree with everything you say but would add that those buying second hand have no voice at all in the discussion, and they are the ones generally getting the problems.

 

[NormanS]

The cast iron exhaust elbow on my Volvo MD22 was showing signs of old age. I made up a mild steel copy, so that if it failed I wouldn't be stuck. I bought an aftermarket one, and was surprised to find it was cast in some aluminium alloy. So far it's been fine, but I've no idea what its life expectancy will be.

 

[Neeves]

Realistically though, how many people buying a new yacht ever actually get to the stage where this affects them? I agree with everything you say but would add that those buying second hand have no voice at all in the discussion, and they are the ones generally getting the problems.

I do agree. its nice to know that there are people who buy and sell their yachts with the frequency some people change their cars. It keeps the second hand yacht market refreshed and as you suggest for the original owners their elbows are never serviced.

We are one of the exceptions and have owned Josepheline for over 20 years now. We did look at buying bigger, ours is 38', but a bigger cat, 45', would cost twice as much, accomodate the same number of people (they would have more space) and all the consumables, sails, cost twice as much. All very nice but we are sufficiently selfish not to invest in the newer yacht to increase the comfort of guests. If they find space on a 38' cat constraining - they don't need to come.

In the 20 years of ownership, I'm guessing, we have bought 2 new elbows for each engine - we have had to remove the scale (calcium) that blocks the elbow with acid but find we can only do this once and then corrosion causes the elbows to fail. Its really not a big issue, nuisance, but it is annoying that such a simple device costs so much and could be made to last longer. But like replacing sails, halyards, filters and antifouling - elbows are just another cost we have learnt to accept.

We accept we need new tyres on a car, we are increasingly going to accept replacing, very, expensive batteries in EV - elbows are just part of the price of ownership.

Take care, stay safe

Jonathan

 

[niallw70]

Bronze works well! I ordered a new exhaust injection bend from Vetus as the original cast iron one was falling appart after 13 years. I was surprised to find the replacement from Vetus was cast bronze, exactly the same design. This year I removed it for inspection while working on the heat exchanger and after 18 years it was excellent on the inside! No dezincing at all so it is obviously not brass. Hopefully good for another 18 years!

Thanks Plum, but I've been looking for this product from Vetus, but can't find any mention of it, let alone a dealer who stocks it.
Do you have details of product, code, description, supplier etc.

 

[Tranona]

Thanks Plum, but I've been looking for this product from Vetus, but can't find any mention of it, let alone a dealer who stocks it.
Do you have details of product, code, description, supplier etc.

That will only be for a Vetus engine which is very different from a 1GM. Your best bet is the aftermarket stainless elbow I linked to in post# 3. If you regularly check the elbow it really is not a big issue. There are tens of thousands of 1GMs running around the world, and although the design of elbow is not the best, other engines are often no better. The premature corrosion reflects the way we use our engines in small yachts - short runs followed by long periods of inactivity.

 

[Plum]

Thanks Plum, but I've been looking for this product from Vetus, but can't find any mention of it, let alone a dealer who stocks it.
Do you have details of product, code, description, supplier etc.

I just ordered the correct part number for my Vetus M3.10 engine Exhaust injection pipe . There was no inducation as to what material it was made of. The original was cast iron and the new one was bronze. Delighted! There was not a choice. I was just illustrating that someone does make them in bronze.

Www.solocoastalsailing.co.uk

 

[niallw70]

That will only be for a Vetus engine which is very different from a 1GM. Your best bet is the aftermarket stainless elbow I linked to in post# 3. If you regularly check the elbow it really is not a big issue. There are tens of thousands of 1GMs running around the world, and although the design of elbow is not the best, other engines are often no better. The premature corrosion reflects the way we use our engines in small yachts - short runs followed by long periods of inactivity.

I agree design not the best. For me the location of the inlet hose connector for coolant water is too near the cylinder head, affecting engine operating temperature. Why do they design these engines to kick in opening thermistor valve at only 60deg C. Anyone with a diesel car knows optimal engine coolant temperature is about 90DegC.
So let's start a campaign to get the coolant hose connection further down the elbow. While I'm at it, also a little hinged flap to cover the end of inner tube, should prevent the tendency of hot exhaust water to back up into the cylinder head when engine is stopped. It probably would need a little spring mounted on flap to ensure flap closed immediately after positive exhaust gas flow ceases. But then it's probably a fine line between being strong enough to close but then retarding gas flow and giving loss of engine power/performance.
I'd be interested to hear from anyone who's attempted to fit some type of one-way valve/ flap to an exhaust elbow to overcome the backflow problem.

 

[Spirit (of Glenans)]

I agree design not the best. For me the location of the inlet hose connector for coolant water is too near the cylinder head, affecting engine operating temperature. Why do they design these engines to kick in opening thermistor valve at only 60deg C. Anyone with a diesel car knows optimal engine coolant temperature is about 90DegC.
So let's start a campaign to get the coolant hose connection further down the elbow. While I'm at it, also a little hinged flap to cover the end of inner tube, should prevent the tendency of hot exhaust water to back up into the cylinder head when engine is stopped. It probably would need a little spring mounted on flap to ensure flap closed immediately after positive exhaust gas flow ceases. But then it's probably a fine line between being strong enough to close but then retarding gas flow and giving loss of engine power/performance.
I'd be interested to hear from anyone who's attempted to fit some type of one-way valve/ flap to an exhaust elbow to overcome the backflow problem.

Anything like that, subjected to streams of hot seawater, would last about two weeks.
Agreed, they could design the elbow to be longer, with the water injection a little further away from the cylinder head, but you would then have a section of extremely hot exhaust pipe within the engine space, which could have downsides when , for instance, having to lean across the engine to deal with a blocked filter in a seaway.

 

[vyv_cox]

I agree design not the best. For me the location of the inlet hose connector for coolant water is too near the cylinder head, affecting engine operating temperature. Why do they design these engines to kick in opening thermistor valve at only 60deg C. Anyone with a diesel car knows optimal engine coolant temperature is about 90DegC.
So let's start a campaign to get the coolant hose connection further down the elbow. While I'm at it, also a little hinged flap to cover the end of inner tube, should prevent the tendency of hot exhaust water to back up into the cylinder head when engine is stopped. It probably would need a little spring mounted on flap to ensure flap closed immediately after positive exhaust gas flow ceases. But then it's probably a fine line between being strong enough to close but then retarding gas flow and giving loss of engine power/performance.
I'd be interested to hear from anyone who's attempted to fit some type of one-way valve/ flap to an exhaust elbow to overcome the backflow problem.

Raw water cooled engines run cool by design. If they ran at typical automotive or indirectly cooled temperatures the coolant passages would block with salts in a very short time. This can be a problem even at typical temperatures of 60C.

 

[sjdtuk]

I have a Nanni N450. Elbow was alloy and failed in two years and fortunately leaked all over the oil sensor setting it off.
Replaced with stainless. So far so good.

Rest of the engine is good - but that was poor.