Possible cause of white smoke/steam from exhaust!

vyv_cox said:
In the case of Bukhs, of which the DV10 and DV20 always seem to steam, ... A favourite place is the fitting through which water enters the block, behind the flywheel. This used to have very small drilled holes that blocked easily but later ones have bigger holes.
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Vyv - My Bukh DV20 (on a Westerly Merlin) is a constant steamer. I've got rather used to it, but now the boat is out of the water for the winter I think I might have a go at sorting it out. I put rydlyme in last year, which didn't seem to make much difference, so I'll attack this block inlet this time. I've heard that it can be extracted with removing the flywheel, but it looks a bit awkward! Any advice on the best way to get it out, and what to look for when it is, would be gratefully received -
thanks
Steve
 
sgr143 said:
Vyv - My Bukh DV20 (on a Westerly Merlin) is a constant steamer. I've got rather used to it, but now the boat is out of the water for the winter I think I might have a go at sorting it out. I put rydlyme in last year, which didn't seem to make much difference, so I'll attack this block inlet this time. I've heard that it can be extracted with removing the flywheel, but it looks a bit awkward! Any advice on the best way to get it out, and what to look for when it is, would be gratefully received -
thanks
Steve
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It is possible to get the fitting out without removing the flywheel, two possible methods are:
1. Cut an Allen key on the short end so that it will fit the bolts but enough leverage can be exerted to release them if they are very tight
2. Buy a ball-end Allen key of the right size (6 mm? long time since I did it), one of the T handle ones would be handy.

The older fittings, like an old fashioned gas poker, are just a tube with a closed end and many small holes, through which the water passes. These are the ones that salt up. Later ones have fewer, bigger holes that I assume do not clog so much. However, the area in the block through which the fitting passes will also tend to accumulate salts, in which case you may wish you had taken the flywheel off in the first place! I took mine off several times and replaced it using the same bolts, which doesn't seem to have caused any problems.
 
Thanks Vyv for this advice - and for spotting that I meant "without" rather than "with" removing the flywheel! I've got both ball-ended and T-bar Allen keys so I'll give it a pop with the flywheel on first. The flywheel looks bloody heavy and having dinged a toe last week by dropping some loft boarding on it , I'm not keen to repeat the performance with half a ton of cast iron!

I guess there's no harm in opening out the small holes a bit beyond their original size?

Steve
 
sgr143 said:
Thanks Vyv for this advice - and for spotting that I meant "without" rather than "with" removing the flywheel! I've got both ball-ended and T-bar Allen keys so I'll give it a pop with the flywheel on first. The flywheel looks bloody heavy and having dinged a toe last week by dropping some loft boarding on it , I'm not keen to repeat the performance with half a ton of cast iron!

I guess there's no harm in opening out the small holes a bit beyond their original size?

Steve
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I would think that opening the holes up a bit might well be a good idea. I cannot see that there is a negative aspect to this, as when the thermostat opens it simultaneously closes the bypass.
 
I had a similar problem with an MD11C some years ago, and eventually it was found that the exhaust hose had partially collapsed inside, probably a result of an earlier overheating. Once the cause was identified repair was easy and inexpensive.
 
vyv_cox said:
It is possible to get the fitting out without removing the flywheel, two possible methods are:
1. Cut an Allen key on the short end so that it will fit the bolts but enough leverage can be exerted to release them if they are very tight
2. Buy a ball-end Allen key of the right size (6 mm? long time since I did it), one of the T handle ones would be handy.

The older fittings, like an old fashioned gas poker, are just a tube with a closed end and many small holes, through which the water passes. These are the ones that salt up. Later ones have fewer, bigger holes that I assume do not clog so much. However, the area in the block through which the fitting passes will also tend to accumulate salts, in which case you may wish you had taken the flywheel off in the first place! I took mine off several times and replaced it using the same bolts, which doesn't seem to have caused any problems.
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Most of the problematic deposits in raw water cooled engines are carbonates. Essentially the same as the build up in domestic water devices in hard water areas. This happens in outboards as well. Sea water has quite a few carbonate ions and at higher temps than (outside) normal they can be deposited inside an engine. Rydlime should work. I circulated round a mixture of white vinegar and brick cleaner - on a closed system - to and from a large bucket until the engine warmed up (in the yard) . Serious froth so some of the undesirable deposits were being consumed. Continued until the exhaust water was too hot to touch and shut down. Left it half an hour to soak and added / circulated fresh water to remove the mixed acid concentrate. Then displaced to 50/50 antifreeze for the winter. I think every couple of seasons is enough?
 
Well, I smothered the Allen bolts holding the "poker" in with 3in1 and WD40 today, so I hope when I next get back to the boat they might yield to persuasion... watch this space (but breatholding not advised!). How long is the poker, by the way?

(The exhaust hose is OK, I think - I'll check, though.)

Thanks all for the advice!
 
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pagoda said:
Most of the problematic deposits in raw water cooled engines are carbonates. Essentially the same as the build up in domestic water devices in hard water areas. This happens in outboards as well. Sea water has quite a few carbonate ions and at higher temps than (outside) normal they can be deposited inside an engine. Rydlime should work. I circulated round a mixture of white vinegar and brick cleaner - on a closed system - to and from a large bucket until the engine warmed up (in the yard) . Serious froth so some of the undesirable deposits were being consumed. Continued until the exhaust water was too hot to touch and shut down. Left it half an hour to soak and added / circulated fresh water to remove the mixed acid concentrate. Then displaced to 50/50 antifreeze for the winter. I think every couple of seasons is enough?
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Quite surprisingly (well, to me anyway) the insoluble salts are mostly magnesium carbonate, with calcium some way down the list.
 
vyv_cox said:
Quite surprisingly (well, to me anyway) the insoluble salts are mostly magnesium carbonate, with calcium some way down the list.
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In John Steinbecks book " Sweet Thusday " the hero, Doc, based on Steinbeck himself, speaks with a guy sleeping rough on Monterey's beach.

He is a very well educated dropout and he states that a cubic mile of seawater contains enough Magnesium to pave the streets of the world.

True or not, that is perhaps where the Magnesium comes from.
 
Don't know yet if it could be anything as this basic for me, but I topped up the coolant, which was on the lower of the levels, and there was no steam, and the water from the breather was cold, not warm. However, it was only after just under an hour on engine. Will need a longer run to be certain.
 
My observation is that if you have steam coming out of the exhaust, you have a problem that needs fixing. Such issues don't fix themselves and always get worse and more expensive in the end.
 
rotrax said:
In John Steinbecks book " Sweet Thusday " the hero, Doc, based on Steinbeck himself, speaks with a guy sleeping rough on Monterey's beach.

He is a very well educated dropout and he states that a cubic mile of seawater contains enough Magnesium to pave the streets of the world.

True or not, that is perhaps where the Magnesium comes from.
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Salts.gif


As you can see from the above (taken from http://oceanplasma.org/documents/chemistry.html), Magnesium is more abundant in sea water than Calcium. That's a little surprising as their crustal abundances are similar (calcium is more abundant), but of the same order of magnitude.
 
AntarcticPilot said:
Salts.gif


As you can see from the above (taken from http://oceanplasma.org/documents/chemistry.html), Magnesium is more abundant in sea water than Calcium. That's a little surprising as their crustal abundances are similar (calcium is more abundant), but of the same order of magnitude.
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Thanks for that.

Who has the skills to work out exactly how much magnesium there is in a cubic mile of seawater-purely as an academic exercise.

Any clever clogs on here want to give it a bash?
 
AntarcticPilot said:
As you can see from the above (taken from http://oceanplasma.org/documents/chemistry.html), Magnesium is more abundant in sea water than Calcium. That's a little surprising as their crustal abundances are similar (calcium is more abundant), but of the same order of magnitude.
Click to expand...

The explanation may be that Mg is easier for river water to leach Mg out of Mg-containing rocks (dolomite?) than it is to get Ca out of Ca-containing rocks (limestone, etc.), so more of it ends up in the sea. Given that alkali earth metals get more reactive as you go down the periodic table, it's possible that Ca ions bind more strongly than Mg ions do to CO3 ions.

Back to the question of why it's Mg salts that block up engines rather than Ca salts; that depends, I should think, on the variation of solubility of CaCO3 and MgCO3 with temperature. I've had a quick dig around but can only easily find info on CaCO3... I'll ask a proper chemist when I next run into one (I stopped doing chemistry in my 1st year as found it wasn't just antipathy to my schoolteachers that made me dislike the subject - it was chemistry I didn't like!).

Steve
 
I get 5.3x 10^9 kg Mg per cubic mile seawater - basically the same.

On a rough calculation, this might cover the world's streets to a thickness of about half a millimetre... [I did start doing a post to show my working, but accidentally deleted it...]. More plating than paving!

Steve
 
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