White smoke/steam at WOT?

Nick_H

Nick_H

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Did a short run at WOT to check max speed with clean hull and stern gear after anti fouling. Everything was good, reached 2300 rpm on D12's, pleased with 29.5 kts as I had half fuel and full water and I've only ever had a fraction over 30.

Engine temps rose a bit of course, but settled nicely just a few degs higher than cruise and well below the redline on the gauge, however I did notice quite a bit of white smoke or steam from both exhausts. It's a while since I've run at WOT, and I honestly can't remember if I've always had this smoke.

Is it normal?
 
Nick_H said:
Did a short run at WOT to check max speed with clean hull and stern gear after anti fouling. Everything was good, reached 2300 rpm on D12's, pleased with 29.5 kts as I had half fuel and full water and I've only ever had a fraction over 30.

Engine temps rose a bit of course, but settled nicely just a few degs higher than cruise and well below the redline on the gauge, however I did notice quite a bit of white smoke or steam from both exhausts. It's a while since I've run at WOT, and I honestly can't remember if I've always had this smoke.

Is it normal?
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I notice the same when the water & air temp is cooler.
 
What is the water/air temp down there at the moment , I would think it would show up more if temps are colder than normal . IE hot moist exhaust gas over cold sea water ? . Same as sea fog effect maybe , or I`m talking c@bblers .
 
I had a run out yesterday in Christchurch Bay, flat as flat can be. Gave my boat the beans at WOT to see what she'd do..managed 32 knots with clean bum, full fuel and water so pleased with that.
Also had plenty of white steam from exhausts at WOT and just normal levels at cruise speed. Put this down to cold water temps at the moment as I think is probably the same reason for your boat too.
 
Nick there is a world of difference between white smoke and water condensate. If the engines seem fine and you got 29.5, and bearing in mind they're indestructible D12s, then it was most likely condensate, which is fine. As others say, was the sea or air cool? Even if not, the WOT running would tend to make condensate more than cruise running (was the white WHILE running at WOT or afterwards?)

White smoke when warmed up generally means unburnt fuel as opposed to partially/badly burnt fuel. To have unburnt fuel you'd have to have something bad with the engine, and with D12s and your 29.5kts that just doesn't sound plausible, so I'd be confident you're in the nothing to worry about category

You there Saturday?
 
Thanks all, it's not that warm here yet so it seems likely it was just steam. It only happened at WOT, and stopped immediately I throttled back to cruise. It also disappeared almost instantaneously, whereas I suppose smoke would linger in the air, so I'm now even more sure it was just steam.
 
Nick_H said:
Thanks all, it's not that warm here yet so it seems likely it was just steam. It only happened at WOT, and stopped immediately I throttled back to cruise. It also disappeared almost instantaneously, whereas I suppose smoke would linger in the air, so I'm now even more sure it was just steam.
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If you threw sea water at 15deg C into exhaust gas at 500 deg C what would you get at the exit? = steam.
 
volvopaul said:
If you threw sea water at 15deg C into exhaust gas at 500 deg C what would you get at the exit? = steam.
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Will this show up more on a shaft drive as exhaust is near surface.. I was out with a boat on legs and I had steam and he didn't ... Temps were good, exhaust elbows were cool so could not find a good reason.. Boat did it all the time for 4hr run .. No oil or water used and ran very well ????
 
Will steam be worse on shafts as exhaust in near surface... I was out with a boat on legs and I had steam and he didn't...
I checked exhaust elbow and all temps and all was well but had steam from both sides.. It was a cold day
 
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