D2-55 New Exhaust Elbow?

[geoff]

Not had it off since the repair, but having used this stuff on car exhausts many years ago it withstands pretty much any thing and sticks like s%$t in blankets. Geoff

[MagicalArmchair]

It sounds a damn sight cheaper than the adventure @Seagoon had here too: http://bavariayacht.org/forum/index.php?topic=1352.0

I'll travel along this route and see how it goes!

[MagicalArmchair]

This stuff I have purchased is rated to around 240 degrees C... the exhaust at that point reaches a staggering 570 degrees C, making it technically underrated.



Back to the lapping option then I think...

[Markus]

This stuff I have purchased is rated to around 240 degrees C... the exhaust at that point reaches a staggering 570 degrees C, making it technically underrated.

While technically at 3000 rpm it seems that exhaust gas can reach 570 °C, please note that this is the gas temperature and not solid temperature. With water injection point being quite close to this area and with the thick-walled parts that conduct heat quite well, my gut feeling is that it should be fine - but do not blame me if it does not hold... 

If you consider the lapping option, make sure there's not internal cooling channels in the area as it looks to me you would need to remove a lot of material, maybe around 10 mm or so.

[Yngmar]

Ouch, that's an unfortunate find. 

Agree with Markus, it seems unlikely that the exhaust elbow gets to such high temperatures - the heat exchanger manifold itself is also water cooled and aluminium conducts heat quite well (epoxy with metal shavings much less so though).

Holts Firegum is rated for 1000°C, but it's just a heat setting paste with no structural strength, so it may or may not be suitable to fill a gap that large. If the gap however could be reduced somewhat by machining down the flange, it might do the job. You'll have to clean up the corrosion to sound metal anyways.

Either way you'll probably have to get those bolts out, which could be a bit of a challenge itself. So while you think about how to proceed, spray some of this on (works on stuck cushion zippers as well): https://wd40.co.uk/product/fast-release-penetrant-spray/

Good luck

[MagicalArmchair]

Thanks all, and thanks Yngmar - It's a boat - something is always broken somewheres! I am bloody glad I checked though, crikey. If anyone hasn't had theirs off, get it off - it took me ten minutes to drop the elbow off, and may have saved the engine.

So, new plan, whist epoxy would probably hold, given the rated max of 240 degrees C and a potential for greater temperatures, I've decided to resist the urge to epoxy it and take the rapid route and will drop it off this afternoon.

A local engineering firm with pressure test both the fresh water and raw water sides of the unit, and then, as they specialise in ally welding, try and weld up and polish up that flange. If it doesn't hold pressure... the quote for a new one in £2,500 ... Christmas cancelled my friends!!

[markram]

Question - we replaced our clogged up elbow with a stainless steel one about 6 months ago. We have not checked it since as I see no reason to after such a short period, but, has anyone any experience with galvanic corrosion using the stainless steel elbow after a period of time? I understand that due to the two different alloys, this can be an issue, although we have checked another engine which had the original elbow (non stainless steel) and there was corrosion as well on the heat exchanger.

[MagicalArmchair]

Hello Markram, it really depends. When I got the stainless steel new elbow from Parts4Engines it came with TWO gaskets - it was supplied to Parts4Engines with a STAINLESS gasket, Parts4Engines supplied a composite gasket. I spoke to their technical department and they said due to galvanic corrosion, they supply the latter and we should bin off the stainless gasket that came with the new elbow.

If your gasket was METAL - check and replace, if it was a cardboard looking composite thing, you should be protected.

[markram]

Thanks magicalarmchair - will definitely check that. What is interesting is that even with the original elbow there was galvanic corrosion on the heat exchanger - you would think that the manufacturer would use similar alloys to avoid this. But then again he would sell less spare parts I guess...
Thanks again

[aquapore]

I am not sure that stainless is the complete answer.
The problem is carbon deposition.
I had the problem a few year ago and hammered, ground and burnt the carbon back to bare metal which was pitted but sound.
I epoxy coated the elbow by immersion with a thick epoxy paint and refaced the sealing surfaces without breaking through the epoxy coating.

The idea was to create a very smooth epoxy finish in the hope that the carbon will not stick to it.

A week ago I took the elbow off and found it covered in carbon. I will attempt to clean it to see if the effort was worth while.

Will advise.

Regards

Aquapore

[ICENI]

Years ago I used JB weld on an alloy part of my Yanmar engine.   The repair was excellent and the damaged gearbox housing lasted right through until I replaced the engine.   Later someone wanted a working Yanmar gearbox so it was sold and is functioning fine!   JB weld I found really good.

[Joe]

I came across the Volvo-Pentra Neutra Salt flushing concentrate https://www.volvopentashop.com/epc/en-US/Details/AccessoriesCatalog/5627?path=1532%2F1961%2F5626%2F5627 which is supposed to dissolve salt and prevent rust and corrosion mainly in saltwater cooled powerboat engines. Wouldn‘t it be a good idea to flush our cooling system with this concentrate at least if the boat is not used for longer periods?

[Craneman]

Hi Just looking at the Exhaust Elbow how many hrs are on your engine? Also how hard do you run it? The reason for me asking is i have a D1 30F with 650hr, and it would appear this has not been remove yet.

[symphony2]

The normal cruising RPM for a D1 30 is 2200+ and you should be able to get around 3100RPM at maximum with a clean bottom. It is good practice to periodically run at maximum for a short period, say 10-15 minutes as this helps burn off the carbon and oily deposits in the elbow. This is particularly important if you do a lot of low load hours or just run the engine for short periods at a time. The life of the elbow is as much usage pattern related as total hours. My last boat was used as a charter boat for most of its life and still had the original elbow at 13 years and over 3000 hours.

Your 650 hours is less than 100 hours a year and typical of "weekend" leisure usage where the proportion of low load, short run time is high so suggest it is well worth removing the elbow to check it. I also have a D1 30 in my new boat with 350 hours in 5 years. I try to remember each time I come back from a trip to motor the last couple of miles up the harbour and 10 minutes of 3000RPM.

[kavok]

https://forum.amicidellavela.it/showthread.php?tid=130304

[PhilBav38]

Hi Just looking at the Exhaust Elbow how many hrs are on your engine? Also how hard do you run it? The reason for me asking is i have a D1 30F with 650hr, and it would appear this has not been remove yet.

I have a D1-30f too, on a 2009 boat with 600-hours, and prompted by the forum I removed the exhaust elbow today for inspection. Elbow clearly needs replacing, which is fine - will upgrade to stainless.

Unfortunately significant corrosion at back end of heat exchanger, as show in photos. Assuming this will need replacing too, although I know how much they cost so still coming to terms with this news ...!

[IslandAlchemy]

That doesn't look too bad to me.   Just clean up the mating face and put the new elbow on.

[MagicalArmchair]

The main thing is that there are no gaps around the flange where exhaust gases could escape so I reckon your prudent check and replacement of that exhaust elbow would be enough. Make sure that you use a composite gasket between the aluminium heat exchanger and the stainless new elbow to limit the possibility of galvanic corrosion continuing should water once again make its way back up to that point.

How will you proceed? Well done for taking the initiative and checking!!

[PhilBav38]

Thanks both - having offered the gasket up dry, there is still a reasonable amount of surface so relieved to just replace the elbow. Which I will do this weekend, before adding ‘check exhaust elbow’ to my routine maintenance list!

Also have a new Darglow Featherstream prop to fit, so looking forward to a motor as well as a sail - it’s been a long lockdown winter!