More steam than usual coming out of exhaust pipe

[Jimbob]

So

Inboard Diesel engine
Checked
Compression of cylinders –ok
No leaks
No water in oil
Changed impeller and thermostat
No water loss from fresh water tank

Water seems to be circulating in an out (raw sea water). Changed the U bend.

Issue seem to be more prevalent when motoring, any tips or checks to make?

[biffer]

Are you sure it's steam and not smoke

[Jimbob]

pretty sure its steam

[biffer]

The only other way for white, lets say fumes , is a crack in the manifold, it would have to be a funny crack in as much it could only be between exhaust and seawater and I'm not sure that's even possible as the seawater only enters the exhaust system at the exhaust elbow.
It could still be white smoke, dark smoke is lack of air and white smoke is lack of fuel, you might have a bug in the filter that's restricting the fuel slightly.
Try running the engine straight off the pump from a fresh bottle of derv

[Jimbob]

Biffer

a very good point - i will check and thank-you

[Peter_C]

When I owned an inboard there are days you couldn't see the steam and days I would look back and go "What is wrong with my boat?" The colder the morning the more steam that was produced. This was not an issue at all, just had to do with humidity and temperature of the surrounding air.

Unless you overheated it recently, and it is running well, I wouldn't worry about it at all.

[biffer]

I would check your fuel system before you stop worrying it

[Peter_C]

Originally Posted by biffer

I would check your fuel system before you stop worrying it

Well you would be able to smell fuel big time, and it probably wouldn't be running very well.

[biffer]

Originally Posted by Peter_C

Well you would be able to smell fuel big time, and it probably wouldn't be running very well.

Not so. We are talking about air fuel mixture. Explain how you can smell that.
You would have to run it a sustained high revs before you could determine whether it wasn't running right and then with a restricted flow. (Which is the white smoke). As soon as you come off revs it stops running rough.
This ain't the first time at this

[m chappelow]

You dident mention you changed the fuel filter in your list think I would have changed that first before doing compression tests
could just be a restriction at full flow or a faulty injector
what did the cylinder compressions say in your test

[chris.moody]

We had lots of steam from the exhaust with our inboard diesel, and we would occasionally overheat. Changed & checked lots of things, eventually found it was wear on the impeller housing cover. After replacing the impeller housing cover the amount of steam reduced dramatically.

[biffer]

Originally Posted by chris.moody

We had lots of steam from the exhaust with our inboard diesel, and we would occasionally overheat. Changed & checked lots of things, eventually found it was wear on the impeller housing cover. After replacing the impeller housing cover the amount of steam reduced dramatically.

I looked at this and thought. Bollox. But actually this is feasible. If the exhaust elbow is starved of your cooling water this would happen. That's probably why we all have exhaust temperature alarms fittied

[chris.moody]

Surprised me as well. In the fault finding we had:

Replaced impeller
Replaced thermostat
Checked pipes from water pump to thermostat for blockages
Checked exhaust for blockages
Replaced exhaust elbow

I was starting to run out of ideas, then inspected the impeller cover and it was very worn (from the rotation of the impeller spindle). Turned the impeller cover over so he worn side was now on the outside and no more overheating, much less steam, and greater water flow from the exhaust.

I was really not expecting the solution to be as simple as that, shame it took 3 months of overheating before I found the solution.

Chris