White steam / smoke

Thanks Nutty,

Will perform those tests this weekend. I replace the impeller this spring. The one I took out was completely in tact (in pretty good shape). The pump itself, I don't know.

Trying to think through logically, if the pump takes longer then 20 seconds to fill the 5 gallon bucket, then pull the water intake line off the pump side of the trans oil cooler and test again emtying the bucket to pin point the raw water pump or a restriction before that point?

Doc, I'm trying to take a logical approach to bwill's issue. To quote him he said "Engine temp never gets over 160, but risers can get hot (wouldn't want to keep my hand on there for real long)." I took that as him saying that he CAN touch the manifold but wouldn't want to hold his hand on it for a very long time. This to me doesn't sound like it's that hot. So maybe there's a difference in the way we two are interpreting what he is saying.

My current boat is a 95 Malibu with a 350 Magnum Mercruiser. Yes the manifolds on this boat are quite a bit different than the PCM ones. However, my last boat (88 Ski Centurion) used the same type manifolds as the late 80's PCMs. When I first bought this boat I pulled the manifolds and cleaned them up and pressure tested them then replaced the riser gaskets. I have looked inside the risers and I know how they work. Water from the cooling system flows through the outside passages to keep them cooled. However, the manifolds and risers are made of cast iron which conducts heat (from the heads and exhaust). So you can't expect them to always stay as cool as the water that is flowing through them.

One more point about steam,.... if water can come out of the facet at 140 degrees with a little steam in its presence, why can't it come out of your boats exhaust at 160 degrees with a little steam?

Nutty,

Are both of those tests at idle?

Thanks

bwill, disconnect the outlet from your raw water pump and let it run into a 5 gallon bucket while your boat is in the water. Only run the engine for a few seconds. In 20 seconds or less the bucket should be full.

79, yes the motor box was up, my engine is painted black and the sun was high in the sky at this time. My engine was hot without having even ran that day. But I still don't think that there is a problem because I or bwill can't hold our hands on our manifolds all day. I'll agree that at idle and under light loads that they will be cool to the touch (and mine are). But under loads, everything including the manifolds will heat up. Water circulating in the block is kept in the block until the thermostat opens. If the water is 160 deg coming out of the engine and mixed with hot exhaust from the riser, I would think that the riser could reach hot enough temps to feel uncomfortable at times.

Think about this,....how hot is your water heater in your house set to. I bet it's not over 140. Can you take a shower with your water set all the way to the HOT setting? Also, next time you pour yourself a cup of coffee, look at the steam that emits from the cup. I'll bet that's no more than 160 degrees either. Just a few thoughts! Brian

Nutty, there should be no steam or water vapor coming from the exhaust, period.That water, dumped from the cooling system should only be 160 degrees, or whatever thermostat is in the block,i suggest a 140.
Don't matter where you are and how hot the outside temp is, the riser should be COOL TO THE TOUCH,if yours are not you have issue also.            boat dr

boat dr- what sealer, if any...do you like for riser gaskets? pcm 454 and sorry to interupt...thanks

I don't think you have anything to worry about. It is normal for some steam to come out of the exhaust with the water. Your temp gauge reads average temperature. There are pockets in the cooling systems (mainly in the heads) where temps will get hotter than the temp gauge is reading. Also, water does not have to reach 212 deg F before it starts to evaporate. 212 degrees is the boiling point (at sea level). Steam can be produced by water evaporating from the road or your driveway on a sunny day.

You stated that your engine is running fine, right? If it makes you feel better, you can unbolt your manifolds from the heads and look for water trails (rust) in the exhaust ports.

Have about 25 hours on a rebuilt engine. Whenever I take off, I get some white steam or smoke from the exhaust for a few seconds. If I am going quick, it will continue, but smaller amount. Yesterday, it seemed to be just a little more then usual.

I have read in other posts that this is water related. Manifolds and risers are new with the rebuild. Engine temp never gets over 160, but risers can get hot (wouldn't want to keep my hand on there for real long).

Does the steam / smoke mean water mixing with exhaust too soon (leak somewhere)?

Could I not be drawing enough water - enough to keep engine temp OK, but not enough for manifolds and risers - thus normal water in manifolds and risers is creating this steam.

Just in case it matters: Engine seems to run fine. Does not have mufflers.

Thanks all!