KAD32 Black bubbles everywhere - is something wrong?

[RIN]

In preparation for changing the oil in my Volvo KAD32s, I put the engines in opposition whilst on the berth to heat the sump oil - about 1200 revs. I did this for 15/20 mins whilst I made a phone call below. When I came out into the cockpit, there were astonishing quantities of dirty black bubbles everywhere in huge clumps. The river current kept a huge circulating this mass behind the boat, other bits escaped and went down the pontoon covering the waterline of other boats.

The boat will occasionally produce smoke when it has just been started but very little

I did clean off the waterline of the boats I had polluted. It was not oil and came off with a single wipe.

Is this normal? could I have some sort of problem? Or have I only noticed this because the boat was stationary? The river bed is mud but the depth gauge was indicating over 3 Metres underneath the boat.

 

[jhr]

Was it high water? Maybe the outdrives (presumably) gathered some mud in the exhausts (assuming they're like Mercruisers and have the exhaust in the legs) at low water and it was expelled by the engines starting up? Mind you, I'd expect them to clear in a couple of minutes, rather than 20.....

 

[enterprise]

Probably the water that had been sitting in the engines heat exchangers before startup, this would turn black because its been starved of oxygen, then airated again once ejected and mixed with exhaust gas at the injection bend on its way out.

 

[volvopaul]

Hi Richard, as you have ran the engines under load but below the rpm of the superchargers the engines will produce smoke and soot, quite common for kad 32s, dont worry.

 

[RIN]

That's a relief Paul, I thought perhaps a turbo had failed. I just wish I had a camera with me it was quite a sight