Another Water in oil sump incident

[Guest]

My engine is a Yanmar 2GM20 sea-water cooling unit. It worked perfectly in the past 17 years but suddenly, it could not be shooten up one day.

After repeated attemps, it finally shot up but need to maintain 3/4 throad to keep it running (any lower level, the engine shutted down automatically). When in geared, the rev is slow and boat speed only 1/4 of normal performance.

I then motor sailed for 4.5 hours. At the end of the trip, with engine stopped, oil was found on the cabin floor. Opened the engine box found "Grey" coloured fluid(instead of normal "black" coloured oil) "jetting out" from the oil level dip hole.

Cleaning up task pumped out 5 liters (it should be only 2 litres !) of solid-grey coloured fluid, which is not sticky as oil but flows more like water.

Replaced the oil with new and then run the engine again found it shooted up smoothly. After a 5 minutes run, checking the oil found
* oil became solid grey colour again.
* volume of oil remained the same.
* fluid flows like water.
* water droplet found in the oil checking cap.

Any advises on what's wrong and how to clean up the engine ?
Will the engine be demaged by the sea water and need over-haul?

Thanks in advance.

 

[Trevor_swfyc]

After 17 years of trouble free use might it not be telling you nows the time to get a part exchange deal on a new one. Expensive but technology moves on, most engines are now fresh water cooled. You could spend a lot of time and money on your engine but who knows what damage has been done or how much corrosion from 17 years of salt water cooling has occurred.
I suppose it all depends on how flush you are.
Your question will salt water cause damage, water/air/metal I think they call it going rusty.
All the best
Trevor

 

[Guest]

my engine is a yanmar 2 gm which failed me after 12 years use. in my case the water injection at the exhaust manifold had corroded through, and the water had then corroded the exhaust port itself and entered the return flow of oil from the cylinder head. result was an emulsion of oil in the sump.

the problem can be avoided by inspecting the exhaust manifold and replacing it after some years use

however, when i removed the cylinder head, i was astonished at the condition of the block itself. there was no significant corrosion despite raw watercooling, and i did not hesitate to install another raw water cooled engine. my confidence was confirmed by the fact that i was offered more than £1000 part ex for my old engine even when the supplier knew what had happened to it.

i suspect the reason is that the small yanmar engines are purpose designed marine engines and not converted kubota tractor engines

 

[Col]

Certainly worth taking cylinder head off first, before you condem it.
Might be just a head gasket.

 

[vyv_cox]

If your Yanmar has the same arrangement as my 3GM30, the water pump is separate from the block, eliminating it as the source of the leak. I doubt whether a problem with the manifold would cause a problem such as yours when the engine was running constantly. Therefore you have a leak between the block coolant and the oil side, that could be a range of things from a cracked block to loose cylinder head bolts. Suggest you take the head off and inspect.

So far as damage to the engine is concerned, circulating seawater around the oil system will not have done it any good, but possibly the damage is not too severe. This is such an easy engine to work on that changing the big-end and main bearing shells would certainly be justified.

 

[johnt]

Im surprised at you VYV !

the most likely cause of this problem is head gasket as has already been said ........

but exhaust failure is a posibility

anyhow .......strip down ..head off in situ is possible ..but in this situation bearings will be suspect and that means engine out ..the crank cant be removed with the engine still in position as it comes out of the back of the block..not from underneath ......as does yours VYV!

this engine will most likely be a GM 13 which may mean dry liners and quiet frankly after running 4.5 hrs on sludge ..........the best thing to do is a complete rebuild and it will be well worth doing !

if you do most of it yourself the engine will be like new if its done properly and will cost under £1000..thats bearings, valves, rings, injectors gaskets, head skimmed etc

 

[vyv_cox]

Who said the engine would not need to come out? It would be a very fortunate owner who could change bearings without removing the engine. In view of the relatively short exposure to water I would replace the bearings without pulling the crank. I would be very surprised if the liners needed to be replaced. In the past I have freed up car engines that were rusted solid for more than a year and they ran with perfectly good compression.

 

[Guest]

Thanks for your comments, guys.

The Yanmar dealer suggested to take out the engine, check damage and then overhaul it, which cost about 2/3 of a new engine. I just wonder whether it is necessary for an over-haul and to replace so many parts.

The water-logged fluid only stated in the engine for 2 days. I have then pumped out the fluid, applied new oil and ran the engine with the sea cock shutted for a while, then pump out the fluid again. This short dry run was done twice but inspection of the interior is yet to start. Do you think that the demage could be reduced ?

I just wonder whether it is possible to have the problem (gasket?) rectified and then re-use the whole unit as it was running perfectly before and the water only stayed for a short period. Of course, we could only know the answer after the inspection.

Arthur

 

[vyv_cox]

Very difficult to predict, especially not knowing the condition of the engine beforehand. Assuming that you find the cause to be the head gasket, you will have an opportunity to inspect the bores and measure any wear whilst the head is off. If the condition is good I would put the head back on and run the engine. Check oil pressure hot and cold with a gauge, which will give you an indication of bearing condition. You may be lucky, you may not. However, you won't have lost anything by reinstalling the head as you won't have to take it off again. Don't run the engine for long if oil pressure is low or there is a lot of bottom-end noise as you may be damaging the crankshaft.

 

[Guest]

The condition of the engine was excellent before the incident. After I replaced the problem fluid with new oil, the engine fired up instantly, ran smoothly and sounded normally during the short dry run period. But the new oil changed to grey colour again after the short dry run.

Anyway, see what will look after inspection.

 

[Col]

I would say you have a good chance of getting away with it due to prompt action on yor part. Certainly worth a go.

 

[Andy]

Yes..thats easy. Go back and read all the replys i got ref 'water in oil' then after two weeks you will still have no idea whats causing it!!!
Im still confused with mine..
Although from the experiments i have seen in my girlies lab , it only takes a tiny ammount of water in the oil to emmulsify it.

 

[johnt]

2 points

1: the engine was run for 4 and a half hours with water in it !

2: 5 ltr's of sludge came out afterwards! thats 3 litres of water!

this isnt a small leak !

no VYV I didnt say it would need new liners I just pointed out that this appears to be an early engine and it might be fitted with them ..later engines dont have liners and are reborable.

With this history ...im doubtfull that just a change of gasket is advisable. you have run for over 4 hours with the engine lubricated with water !

to me this means all wearing surfaces need to be examined ,
starting with the oil pump , the camshaft, cam followers, tappet faces, big ends , main bearings, all need looking at, the pistons and liners should be ok after honing , but you would need new rings, if you are at all mechanicaly competant you can do a complete rebuild for under £1000

the alternative is to go for the head gasket/exhaust stub change (thats about £150 for parts) ...but dont be surprised if two weeks later your bearings fail

if its 17 years old your exhaust stub will almost certainly have pinholes in it and needs changing even if it isnt the cause of problem

for a better idea of the size of the job ..look at September last's Practical Boat Owner theres an article in it on stripping and rebuilding a Yanmar 2GM . I wrote it.

 

[vyv_cox]

I'm not disagreeing with you, but it must be worth a go to spend 150 pounds instead of 1000? The money won't be lost. Reasonable oil pressure and absence of knocking should give confidence that bearings won't fail suddenly.

Years ago I had an Alfa Romeo that developed a terrible water leak after being frozen. Over a period of months I was changing head gaskets very frequently and the oil was almost permanently contaminated with water. Despite this appalling treatment (I had no money to do the job properly) the bearings never gave a moment's trouble.

I'm still interested to know how a corroded water inlet on the manifold could fill the sump with water. How does the water travel up the exhaust pipe when the engine is running? Surely the exhaust gases would blow water out into the boat? That's what happens if the hose clips are left loose. :~)

 

[johnt]

I tend to agree with you Vyv, exhaust pressure should force the water out ...

That leaves the head gasket ..and for a leak of that size I'd say skimming the head is a must

Ive had the opposite to you ..a car with a head leak ..just changed the gasket and ...OHHHHHHHHHH SHI* 2 weeks later
...and as this engine runs with a much higher compression ratio?

anyway head gaskets are somethng like £50

..17 year old engine ..lots of hours ..ITS BROKE .. time to fix it properly!..even down to new anodes....and then you get years more trouble free use out of it

£1000 is is a very pessemistic estimate ..mine cost £1600 including including prop ..controls ..new shaft , fitting etc etc .so this one could possibly be skimped a bit and come out at about £500.

 

[johnt]

oh ..and the £ 1600 included the cost of the second hand engine..£300.