Steam from exhaust

[Jewel]

At revs 2500rpm a substantial amount of steam comes from both exhausts, as well as exhaust water . Amount of steam increases as engine revs increase. The boat is a 1992 Birchwood TS37 semi-disp with 2 no Volvo TAMD41B 200HP diesels. Temp gauges remain at normal 175deg with no increase irrespective of engine revs, indicating that all is normal. Exhaust pipe goes direct from engine to boat rear - does not appear to be any silencer or other boxes in line etc. Have the boat for 1 season and has always been this way. Is steam normal?

Thanks




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[jfkal]

Check the temperature at the mixing elbow. But in general if it looks like there is enough cooling water I would not be that worried. Especially in cooler weather or with high humidity in the air you would get steam. Could however indicate high moisture content in the fuel but not very likely. Make sure it is really steam and not white smoke.

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[Spectre]

I have a similar problem with my Bukh DV20 I have exhausted, excuse the pun, all avenues that I can think of so I have addressed the matter to Pat Manly PBO's engine expert so hopefully it will be answered in the next issue or soon after.


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[bigmart]

A mate of mine suffered this type of problem on a Volvo 2003 Yacht engine. After several months checking the fault was traced to the cooling water pump( integral with engine) that was leaking water into the sump. From the sump it was getting into the inlet manifold & thus the exhaust. I know its a different engine but is this possible?

Martin

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[Will_M]

Your problem my be a result of head gasket failure leaking water into engine as such whats the eng oil like? Does the engine loose water from its fresh water side at all?

Or another poss is manifold gasket or manifold itself having failed and passing water into exhaust system.

It may even be as simple as turbo to manifold gasket having failed.

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[vyv_cox]

If you search this forum you will find numerous posts on Bukh 20 steaming. I am not able to say that every one does it, but every one I have known does, regardless of installation, boat, etc.

The raw water throughput is quite low, the bypass flow is also unusually low and the design of the manifold is possibly unusual. The consequence of all of this is that quite hot water hits the manifold in a way that seems to encourage steam generation.

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[brianrunyard]

If all else appears ok, (engine temp, oil level, no water in oil) I would say there is nothing to worry about.
When the engine is working harder the cooling water has to remove more heat from the engine to maintain the correct running temperature, this hotter water injected into the exhaust is likely to produce some steam, considering the temp of the exhaust gases as they leave the manifold.

<hr width=100% size=1>Brian
http://homepage.ntlworld.com/brunyard

 

[Birdseye]

I agree. its very easy to become a mechanical hypochondriac and imagine all sorts of dire problems.

the products of burning diesel fuel are steam and carbon dioxide. with a slow flow through a water cooled exhaust, the steam will be condensed back to water. when you get big volumes going through, the exhaust is short and un obstructed, and maybe its cold outside, some steam may well appear at the transom. so its not necessarily a problem - might be, but might well not be.

you need to check all the other points such as water in the sump and emulsified oil. loss of power? engine overheating? difficult starting?

i suspect an awful lot of boats will produce some steam under full throttle at this time of year. certainly, mine does and thats a yanmar.

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[samwise]

In certain conditions our Bukh 20 will produce copious qualitities of steam, much to the alarm of my wife who still distrusts the motor following a thermostat failure while trying to negotiate the Walton channel in nasty conditions ( This despite replacement of thermostat and housing and water pump).

Steam behaves very differently from smoke and while all that white stuff may seem alarming I have experienced no signs of distress from the engine, no overheat warnings, emulsion in the oil etc.

I agree that the phenomenon is more likely at this time of year. A recent early morning departure from the Deben had us steaming like a floating kettle!

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[Jewel]

Thanks for all your suggestions and they have given me additional points to consider. As both engines are behaving identically, and with some of your assurances I reckon there is nothing wrong. As one reply said, the effect is much worse on cold days, not nearly so noticable on warm sunny days. All engine readings remain normal. Oil and water levels check out ok with no topping up of either necessary. Instant starting and very little smoke except after starting for the ususal few minutes.


Thanks again

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