white vapour from exhaust

[Talbot]

last time I used boat I noticed that although there was good water flow, I was also getting white vapour.

Engine is a 3GM30

water supply is through the standard gate valve on the SD0 saildrive. I am unable to shut this completely, so have been unable to fill the strainer more than an inch .

My initial thought was that there was a shortage of water (intend to fit independent thru-hull at next haul out)

What else should I be checking?

 

[pagoda]

last time I used boat I noticed that although there was good water flow, I was also getting white vapour.

Engine is a 3GM30

water supply is through the standard gate valve on the SD0 saildrive. I am unable to shut this completely, so have been unable to fill the strainer more than an inch .

My initial thought was that there was a shortage of water (intend to fit independent thru-hull at next haul out)

What else should I be checking?

I also have a 3gm30.
Depending on external air temperature - and relative humidity I occasionally see white vapour in the exhaust. It is vapour / condensation and dissipates in air very rapidly.
I think it is at mainly down to the direct cooling system- the cooling water is exposed to higher temperatures in the exhaust manifold, so exits the aft end with more water vapour among the hot exhaust gases.
I have a good water flow through the system, and as it seems quite weather/temperature infuenced - I'm not unduly worried.

Direct cooling engines are well out of fashion these days, so fewer people may ever notice a misty exhaust.
Your gate valve sounds like it needs attention - or bypassing as you suggest.

Graeme

 

[Talbot]

our explanation is reasonable, except I have 2 of these engines, and would expect both to have this vapour if it was merely external conditions - but it is only the starboard engine that has this vapour.

 

[oldsaltoz]

Diesel fuel will show as a white mist if not fully burnt, usually due to an injector problem.

Simple check is to have the engine running and loosen one injector at a time and the one that makes no change in engine revs or sound is the problem unit.

Good luck and fair winds.

 

[pagoda]

Diesel fuel will show as a white mist if not fully burnt, usually due to an injector problem.

Simple check is to have the engine running and loosen one injector at a time and the one that makes no change in engine revs or sound is the problem unit.

Good luck and fair winds.

Agreed, but you will probably have a horrible diesel film on the water behind you. I have never seen that.
I've put a cold mirror in the mist and it the condensation smells of very little. (and no, I am not about to taste it )

Graeme

 

[Highland laddie]

White smoke

Incorrect injector pump timing can cause this.

 

[Talbot]

Don\t think that this is a specific injector problem, as

no unburnt fuel in water
engine revs are better than other engine (probably because other engine has a bigger alternator)

 

[barnaclephill]

most apt thread

Thank you for this thread. I had these symptoms this morning

Right on sunrise, on the trip to haul-out and antifoul. This white vapour dissipates by about one metre after the exhaust. No film of oil on the wake, and doesn't appear to be water vapour (as in a leaking head gasket). Dawn was very humid with a coldfront/trough overnight.
Engine is a very old Yanmanr YSM8, single cylinder, pushing a 4.5 tonne yacht. The engine has suffered abuse by me, running it till siezed on 2 occasions about 6 years ago, but it usually (for the past 3 years) has no smoke of any colour (neither blue or white or black - except when going in a bar).
A conversation with a mechanic at the yard today discounted that it would be any calcium deposits in the raw water passages, but rather just an old and tired engine. He suggested a "service" starting at a thousand dollars, just to come to a diagnosis.

I don't think it was getting more than about 80% of full revs.
Would it be, as it's only been the past 6 months, the fouling on the hull, or the dewpoint? Or multiple other problems?

 

[affinite]

I have a 3GM30 on my boat in Greece. Last week had lots of "white vapour" aka steam when motoring. Overheat alarm would go off if engine pushed above 2500 revs. Unlike you there was poor water flow out the back. When stripped down I found that the raw water thermostat bypass hose was blocked with calcium type deposits (hence poor water flow even when cold) and the thermostat was crunchy and stuck closed with deposits thus preventing cooling water flowing when hot. Cleaned off and tested thermostat, opened up thermostat bypass hose and problem went away.