Kat-n'-Dawg
New member
I have an 18HP Johnson Sea horse, circa 1958. Cruising around in the pontoon the other day it started spewing white smoke out the exhaust. I*searched all the posts in the archives and what I found was a hot (no pun intended) discussion about white smoke and steam.
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Well, one begets the other. When water is heated to a certain point it vaporizes and turns into a gas that we call steam. You can't see it, and it's oderless (barring any added elements or compounds.) When steam encounters a lower temperature - less than 200-something degrees - it turns into water vapor, also described as white smoke. To see this theory in action, get an old kettle, put water in it, put it on the stove, and when it starts whistling look at the spigot closely. The first fractional inches out of the spigot can't be seen, but a 1/4 to 1/2 inch up you see white smoke. So, when someone says they have white smoke they have water vaporizing. There aren't too many parts of an outboard that get that hot, so we must deduce that water is getting into the combustion chamber, or such.
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So, the questions on this subject are asking for your experience in determing the most likely cause. Head gasket, cracked block, other sources that could be producing that symptom? You can be a rocket scientist or a good ole' boy, but I'll bet someone out there has had a similar problem.
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Thanks for sharing your knowledge - I'd like to know where to start........
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Well, one begets the other. When water is heated to a certain point it vaporizes and turns into a gas that we call steam. You can't see it, and it's oderless (barring any added elements or compounds.) When steam encounters a lower temperature - less than 200-something degrees - it turns into water vapor, also described as white smoke. To see this theory in action, get an old kettle, put water in it, put it on the stove, and when it starts whistling look at the spigot closely. The first fractional inches out of the spigot can't be seen, but a 1/4 to 1/2 inch up you see white smoke. So, when someone says they have white smoke they have water vaporizing. There aren't too many parts of an outboard that get that hot, so we must deduce that water is getting into the combustion chamber, or such.
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So, the questions on this subject are asking for your experience in determing the most likely cause. Head gasket, cracked block, other sources that could be producing that symptom? You can be a rocket scientist or a good ole' boy, but I'll bet someone out there has had a similar problem.
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Thanks for sharing your knowledge - I'd like to know where to start........
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