white smoke or steam

[Alan Wheeler]

Good point Chief. I shall add that to the study hall.

Limmer, you have said you have found bits of impellor. Is this from the current impellor or a possible old one now replaced with new?
Those pieces can get into some very tiney places. But the main area of restriction is actually at the outlet of the pump itself. Pull the impellor and check the outlet and ensure you have no blade stuck up in the gap.
The next point is the heat exchanger. Follow the outlet of the pump to see where it enters the next piece of equipment. Sometimes the oil cooling exchanger is next. This unit is small and could be easily blocked.
The next should be the main engine heat exchanger. This has a series of small tubes that a blade will not fit through. However, there are a lot of these tubes and blocking off a couple with a blade or two will not cause the problem you are finding.
From there, it can go to either a exhaust cooling jacket if fitted and/or the exhaust.
You can check each unit by simply removing the hose and very briefly run the engien to see how much water is pumped. If you have a good flow in one and not much coming out, then that will be the source of the problem.

Depending on the air temp and humidity of the ambient air,

Jef you don't need any help. That's pretty much it. Although air pressure can also have a big influence. Air pressure and temperature is what causes due point, or..the point at which cloud is created out of "thin air".

[Ex-Calif]

Ok - quick review - there are two separate systems. The fresh water system is a closed system. For thoroughness just make sure the fresh water system is full.

Then as Pat has said focus on the raw water system. Water is drawn in to an impeller, it is "pushed" forward through a heat exchanger where the cool raw water runs through tubes and takes heat from the fresh water across the metal surface of the tubes.

There it flows into the exhaust at a mixing point finally being ejected at the stern.

You condensed the steam vapor in a metal bowl and confirmed that it is salty water.

Water is converted to visible steam through too much heat or more correctly a large enough difference in ambient temperature and the vapor temperature. i.e. hot saturated air becomes visible steam at lower relative ambient temperatures. Just like a car exhaust in winter.

So you have visible steam because it is colder outside than you are used to seeing. Or there is less water hitting the exhaust mixer and less water with the same heat = higher vapor temperature @ same ambient temperature = visible steam.

The question of whether it is safe to operate your engine with visible steam is whether there is plenty of water flowing out the exhaust. If there is insufficient water to cool the fresh water system, you will overheat and boil off the fresh water system and then you run the risk of overheating the engine.

You mention that you found debris in the heat exchanger - does this mean the impeller is damaged? In any case if there is "little" water in the exhaust you could have blockage in the heat exchanger that you cannot see. You may have to pull it and get it chemically cleaned - any radiator shop should be able to do this in a chem tank.

[Alan Wheeler]

You condensed the steam vapor in a metal bowl and confirmed that it is salty water.

Ummm, Salt won't "transport" with steam. So the salty water you are tasting (ick!:-) is likely to be what is lying in the exhaust or it is indeed the raw water being blown through.

[Ex-Calif]

I made a couple of assumptions that a) he must have been getting a little "splash" with his steam and b) it didn't smell or taste like burned engine oil.

I've done a fair amount of troubleshooting in my day but I must admit I've never actually tasted my exhaust...