Well, Gary, I would have to believe that the temp problem is related to the impeller and overtemp incident you initially described. And as the thermostat isn't in the raw water system, my money would be on another horse.

You say that the temp finally reached its normal operating value. But I wonder whether there could still be an obstruction in the raw water system. Or there was, but it worked its way out.

Gary

I do not know what overtemp you may have seen when you lost your impeller. Diesels build up heat much faster the gas engines due one higher cylinder pressures and secondly just due to the fact the fuel has twenty five percent more energy in it.

If you are seeing white smoke in the exhaust it will either be that there is not enough cooling water coming from the raw water side of the system and the wet exhaust is getting hot enough to vaporize the water and turn it to steam. The second source is more problematic and I hope this is not what you are seeing. That would be if the engine got hot enough to crack or warp the head. If this is the case and you get water in the combustion chamber it can cause casistophic damage. Water is non compressable and there is very little spare space in the combustion chamber when the piston is at top dead center. The result is often cracked pistons, cracked head and the posibility of bent conecting rods. Check you coolant level, if it is going down after engine use with no losse seen externaly, the coolant could be leaking into the combustion chamber and causing your white smoke.

I will hope that a piece of your failed impeller has lodged somewhere in the raw water side of the system and is restricting flow as Larry suggests causing this steam. You could try and back flush the system, also there have been a few posts regarding restrictions at the nozzle where the cooling water is injected into the exhaust at the exhaust elbow. You can remove the hose to the elbow and make sure it is not obstructed.

I have made the mistake (just once) of running the engine with the seacock closed and fried the impeller in short order. I had to take the hoses and heat exchanger apart to find all the pieces.

I often wonder why there isn't a strainer just downstream of the impeller to catch any vanes pieces. It would need to be large enough to pass sufficient water even after the vane debris lodged there.

Perhaps there is an adequate strainer available that I can add if I ever get the urge.

Gary,
As has been already mentioned, I think you need to take apart the raw water cooling system, and make sure you have every piece of fried impeller. The broken vanes have a nasty habit of lodging themselves in any restriction. Look carefully at all sharp bends, all nipples, and all elbows. It's a pain to do so, but you might still have some pieces in there. Because it's on the raw water side of the cooling system, you won't have to replace any antifreeze.

Gary:

That will be something now that sticks in your mind if you ever see steam coming out the back. We just had a similar thing happen last weekend as we were motoring out of White lake going to Pentwater for the weekend. I sucked up a weed and it was partly blocking the intake hole for the raw water.

I bites us all in the butt at time as first thing I did was to look at the strainer coming in and seen very little weeds no more then usually. So my next step was the impeller. That was fine as I caught it before it got to hot. Usually it runs about 160 and I noticed it was creeping up to 180 so my wife shut the diesel down.

If I had just pulled the strainer off and seen how much water flow, that would have told me what was wrong. Oh well I needed a swim any how.

Glad you finally found out the trouble, now onto sailing.

Randy