oil and water

[schilde]

Is there an oil expert out there?

I fitted some clever valves so that I could flush my sea-water cooled inboard engine with fresh water. When I tested it I left the water running after the engine stopped, and filled the exhaust with water. I realised what I had done overnight but by the next morning the engine had water in a cylinder and in the oil.

I then did two oil changes to get the watery oil out of the engine, and I think the engine will be undamaged.

As I had only just finished a complete rebuild of the engine it and the oil were really clean, apart from the (fresh) water. I heated the oil up in a saucepan and boiled off the water. (carefully!) I heated it very gently to avoid burning the oil. It probably went just a little over 100 deg, maybe 110 or 120.

The question is, is this oil now as good as new? Surely oil must be designed for parts of an engine where higher temperatures will be encountered, so will it be damaged?

The oil is 10/30 and 10/40 4-stroke oil for marine petrol engines.

I know it is cheap to buy new oil but it is a shame to waste it and someone has to pay to dispose of it.

I now turn off the hose before stopping the engine!

Steve

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[bruce]

dump the old oil, run the motor to dry out all the remaining moisture, with new oil in it, drain and repeat. oil is cheaper than the motor to replace. once the motor is up to temp, continue to run to be sure all the moisture is out. good luck...

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[Prospero]

I agree with Bruce - dump the old oil in an enviromentally friendly way. When I had a boat hire business once or twice our clients managed to put the boat not quite under water just enough that water got into the engine. My cure, after pumping out the boat, was to drain the oil and water from the sump, fill the engine with petrol, up to the dip stick mark, and then turn the engine over by hand. This enabled the oil pump to circulate the petrol throughout the engine. The next step was to drain the petrol and water mixture and discard. Refill with oil and run for a short period say 10 hours and then do an oil change. Needless to say change the oil filter every time you change the content of the sump. This worked for me every time and I had no ongoing problems with the engines.

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[Gordonmc]

I would be uncomfortable about using petrol. There will still be explosive vapour in the breathing system after you drain off and its difficult to dispose of.
It would be safer and cheaper to use proper flushing oil from a motor factor or diesel.

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[brianhumber]

As others have said, new oil is cheap enough. However if you are this situation in the middle of the oggin without fresh suppplies and want to get out of the poo, then you can settle out oil from water by just leaving it in a can. Gentle heat, not 100C will make this operation quicker. This works well with traditional mineral oils, I am not aware the modern synthetic oils are water absorbing but perhaps others could comment on this ( some years since the oil industry left me!)
Regards the engine I would not be happy flushing with petrol, suggest flushing oil as water will be left as droplets in oil ways and surfaces through out. As it was fresh, this is not a problem unless left to start the rusting process

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[Avocet]

I'm no expert but I think 120 degrees is a bit hot for most mineral oils - I've a feeling you might have started to "cook" it. I'd be inclined to flush with flushing oil (or the thinnest cheap oil you can find) and then refill with fresh oil. Our local tip don't charge for disposal of oil (in DIY quantities anyway). If its any consolation, our boat sank in salt water (before we had it!) about 10 years ago. This year I did a partial engine rebuild and the main bearings were fine. I couldn't find any sign of water damage anywhere inside the engine!

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[VicS]

I have just revisited this topic and here are my thoughts.

If you have heated the oil as carefully as you say then no harm has probably been done but i am surprised you got away with it without the whole lot exploding all over the place. I am in agreement with those who say its wasn't worth it but if the oil has not darkened and is now clear and bright and free of water droplets it is probably OK. In service oil will locally be sujected to quite high temperatures, on the underside of the piston crowns for example.

You must be certain to have removed all the water from the engine so why not use the old oil as a flushing charge followed by a second flush with a cheap oil of the correct or perhaps lighter grade. In each case run the engine for long enough to be well warmed up then drain the oil immediately. Finally refill with your normal grade fit a new filter and go for a good local run.

Regarding the suggestion to flush with petrol i think this is one of the worst and most potentially dangerous things i have read for some time.

By the time you have filled the sump with petrol you will have the whole boat full of petrol vapour and you will be inhaling a dangerous level of vapour. If you survive this far youve then got to drain it out again, and dispose of it. Youv'e still got a boat and an engine crankcase full of petrol vapour

One little spark during all of this and you and the boat will be gone to the great sailing waters in the sky. Even if that doesn't happen the damage caused to you and your internals by inhalation of petrol vapour could be very serious indeed.

Furthermore, petrol is immiscible with water so will not help to remove it, engine oil, by comparision, will absorb some water.


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[Trevor_swfyc]

Schilde,
I have done similar, that is fitted some clever valve system so that I can use the engine salt water pump as a secondary low level bilge pump and also for fresh water flushing.
Several points you should never connect the water inlet direct to a pressurised supply, you have discovered why.
Secondly you should never heat a mixture of oil and water, glad to hear on this one you did not discover why, you could have been seriously burned when the contents of the pan bumped all over you.
Also the anti wear additive a Zinc dithio phosphate will break down when heated with water giving off hydrogen sulphide so if you escaped getting burnt you could have been gassed.
So dump the wet oil, and as already suggested flush with a cheap oil or flushing oil, run the engine for 5 minutes to get any water into suspension, then immediatly suck it out. Finally add the fresh good oil, a trace amount of water will not cause a problem but you can test the oil after you run the engine for a while with a crackle test. Probably best done on the bar-b-cue, drop a 1 ml sample onto a hot plate at about 120 - 150 c wet oil will crackle, test is sensitive down to about 20 ppm water/oil. Wear eye protection in case it spits in your eye but with your luck you should be fine!

Trevor

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[schilde]

Thanks Trevor!

At our house we rgularly heat oil close to the point where it smokes, then we lob in wet bits of potato and usually get away with it! Lots of people do! But you are right, it's not the same kind of oil. I did have to be a bit careful and I did have one splash that ignited... so you are right, I wouldn't recommend this action.

The oil ended up darker than it went in to the engine, so I think a lot of its life has gone. Ill use it in the oil can for odd jobs, not for the engine.

My engine is an old volvo saildrive that has its water pump down in the saildrive leg like an outboard. So the valves had to be a bit clever in diverting the sea water overboard as well as allowing the fresh water in. And the fresh water does have to be pressurised, because there is nothing to make it circulate. But I have solved the problem by ensuring the hose is turned off before the engine is stopped.

We haven't had a barbecue for a while but after several oil changes I think I have got out most of the water and the engine is fine.

Thank for your reply

Steve

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[schilde]

Thanks Brian.

The whole exercise started because last year the saltwater seal on the driveshaft failed and allowed water into the oil sump. It was a while before I could get the engine out - as it is a saildrive I had to get the boat lifted, and I had to wait until I knew I would have a few weekends free. In the meantime the engine deteriorated and would no longer run. I was not too hopeful.

It turned out that the water had, over several months, caused emulsion to build up which blocked some oilways (including causing the engine to pump out all its oil through the breather once). The valve gear was all covered with rust and the valves themselves were covered in yuck and there was no compression. Apart from that everything was fine.

I also found lots of corrosion and salts blocking the waterways, a separate problem but which made me do the freshwater flushing valves.

I completely stripped down the engine, cleaned everything, re-ground the valves, and re-assembled with new gaskets and seals but no other new parts, and it now runs like new.

Imagine my disappointment when I waterlogged it again!

But it's all ok now, and I've learned a lot!

Steve

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