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Discoloured Diesel in engine

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Hi everyone, 

 

I am in the process of buying a boat. it's in a boatyard and they took the diesel out of the engine to polish it and said it's not worth polishing as it looks like this:

 

does this suggest there is a serious problem with the engine? Should I look for another boat? thanks,

5B1F97C6.JPG

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As long as that stuff hasn't been through the engine, it will be fine

 

And if it did go through the engine, it would stop - looks like it is mostly water

 

Richard

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Do not believe anything that boat yard tells you, if thats clean diesel then what does dirty stuff look like.

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I think they meant it would cost more to polish whats in the tank than it would to dispose of it and put fresh in.

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If the boat has an integral fuel tank at the stern I would inspect it internally with an endoscope through the filler hole. Apart from rust and scale around its bottom and sides there is also the rudder stock tube to examine closely that can rust and corrode away too and quite expensive to fix.

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That is a mixture of diesel and water. It all needs to come out and be disposed of. What Bizzard says is right, you or they need to check, maybe endoscope?, and get rid of the sludge and rust in the tank, If its at all possible it would be good to pressure test the tank to make sure it has not rusted through somewhere. You are not alone, I scrapped a large amount of expensive road diesel a couple of years ago in my boat and it really was a right pain. It shouldn't damage the engine as it simply will not run on that stuff . Mention all of this to your surveyor and trust him to check the tank and the engine. It doesn't write the boat off, there are lots of boats with horrible things in their fuel tanks but their owners don't know (yet)

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What engine? Some are more tolerant of bad fuel. 

But that looks to be all water and rust. Definitely dump it.

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A lot of my customers either have a perished O sealing ring on the diesel filler cap or its missing completely. Worth checking as it could cause what's happened here.

Edited by Liam

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I wouldn't be buying that boat unless, you have a good survey including seeing the engine run off its own fuel supply for a couple of hours. That stuff is probably in the lines filters and injectors, because you can bet someone has tried to start it.

 

  • Greenie 1

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Two problems both serious:

That fuel will damage, in order of contact, everything between the tank, and the combustion chambers of the engine, the filters, fuel pump, injectors, valves and rings.

There should never be water in a fuel tank and operators should periodically check for water in the separator bowl, and I strongly recommend periodically drawing a bottom tank sample into a glass jar to check. I used a basic plastic bulb pump with an extension long enough to bottom the tank operated down the fill point. Any thing more then a few drops of water occuring very rarely warrants increasing your inspection frequency and investigation. It is rare that fuel from a supplier with regular turnover will be water contaminated.

It however is not uncommon to get water ingress through poorly sealed fill points or poorly located tank vents. The checks described above are those carried out daily on aircraft and aviation fuel installations. Tank failures do occur and manifest themselves as either: continuous losses from a standing near full full tank, often with teltale plume and fuel smell in the surrounds such as on the water around a boat, or repeated water ingress into a near empty tank. 

 

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I'd say it depends how exactly that sample was taken. Most diesel tanks have gloop like that swirling about in the very lowest part. Condensation occurs in tanks and drains down to the lowest part, which is why the take-off pipe is not at the very base of the tank. To save picking up this gloop.

 

If the sample was taken by dipping a tube to the base of the tank through the filler, then this is not unusual. If this sample was drawn from the engine fuel lift pump then yes this boat has serious problems with the tank and it needs draining and cleaning.

 

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To me that looks far worse than you might normally get if some rainwater is finding its way past a leaky filler cap.
 

I would be asking serious questions about just how so much water could get in the fuel tank.

If, as has been suggested, the fuel tank is in the counter stern, such that the rudder tube passes through t, I would seriously be questioning whether something in that arrangement is holed and connecting the canal to the tank.

As has been said, if someone has tried to run the engine on this stuff, all bets are off as to how much damage that might have done, and what it might cost to fully sort out.

Be very cautious here, I think.

Edited by alan_fincher

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Strikes me the boat yard have been pretty decent here so I would ask them for their advice. Presume they will say something like  get rid of the old diesel and perhaps change the filter. If that’s fine and the engine runs then the issue is how did the water / muck get there ?  

 

You dont say say how old the boat is and is it in or out of the water ? 

Edited by jonathanA

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10 minutes ago, Mike the Boilerman said:

I'd say it depends how exactly that sample was taken. Most diesel tanks have gloop like that swirling about in the very lowest part. Condensation occurs in tanks and drains down to the lowest part, which is why the take-off pipe is not at the very base of the tank. To save picking up this gloop.

 

If the sample was taken by dipping a tube to the base of the tank through the filler, then this is not unusual. If this sample was drawn from the engine fuel lift pump then yes this boat has serious problems with the tank and it needs draining and cleaning.

 

The amount of condensation is suprisingly small, but if the tank bottom is never drained it will over time accumulate to the level of the fuel draw off, whatever that level is.

That gloop, a mixture of water, dust and pollen, airborne silt, and tank rust, is a fertile breeding ground for diesel bug, so in all likelyhood contains both live yeasts and dead bug. This grunge is also far more corrosive to the tank interior then the diesel wetted surface and the unwetted tank top area.

A common mistake is to assume bug treatment gets rid off all bug grunge, it kills it yes, but dead bug is just as capable of blocking filters. Get rid of that grunge. It is generally not hard to do and should not be there, it is just a latent problem.

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18 minutes ago, alan_fincher said:

As has been said, if someone has tried to run the engine on this stuff, all bets are off as to how much damage that might have done, and what it might cost to fully sort out.

 

As the photo shows rusty water not diesel, the engine will not run on it. So consequently I doubt the OP's assertion this has been drawn from the engine.  I reckon it came from a tube dipped into the tank.

 

If the engine runs, we can be reasonably certain the sample shown was not drawn from the engine and no damage to the engine has occurred.

 

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Just now, Mike the Boilerman said:

 

As the photo shows rusty water not diesel, the engine will not run on it. So consequently I doubt the OP's assertion this has been drawn from the engine.  I reckon it came from a tube dipped into the tank.

 

If the engine runs, we can be reasonably certain the sample shown was not drawn from the engine and no damage to the engine has occurred.

 

 

Yep, I assumed what OP meant was it was a sample from the tank, (I know they didn't say that!).

I didn't say the engine would run on it, I said someone may well have tried to run the engine on it, (and hence it may well have found its way into pumps and injectors).

If that sample is from low down, and it is not that contaminated slightly higher up where the fuel is drawn off, they might have managed to run the engine, (perhaps erratically), and drawn a fair amount of water through it.

I think it is dodgy to assume no damage to the engine is possible, without knowing a lot more of the history, including how that sample was collected, and what the actual mix is of what is, (or is not), in the tank.

  • Greenie 1

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1 minute ago, alan_fincher said:

 

Yep, I assumed what OP meant was it was a sample from the tank, (I know they didn't say that!).

I didn't say the engine would run on it, I said someone may well have tried to run the engine on it, (and hence it may well have found its way into pumps and injectors).

If that sample is from low down, and it is not that contaminated slightly higher up where the fuel is drawn off, they might have managed to run the engine, (perhaps erratically), and drawn a fair amount of water through it.

I think it is dodgy to assume no damage to the engine is possible, without knowing a lot more of the history, including how that sample was collected, and what the actual mix is of what is, (or is not), in the tank.

 

My limited experience of diesel tanks a few years old is if you get a tube down to the very bottom and suck up a sample, it always looks like this. But I agree if this gloop has found its way into the engine (which I doubt very much), then serious damage will have occurred by now. 

 

 

  • Happy 1

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5 minutes ago, Mike the Boilerman said:

 

My limited experience of diesel tanks a few years old is if you get a tube down to the very bottom and suck up a sample, it always looks like this.

 


I must admit I've never been brave enough t go looking in my 80 year old diesel tanks!

However when I suspected issues with Chalice, which had a typical "modern" boat's tank in the counter, and I drew off a sample from the bottom of the tank, it looked nothing like that, being almost certainly "diesel with a bit of something else", rather than "mostly water". That was a near 20 year old boat.  I can't vouch for the first 10 years, but I know that until I got around to looking, I hadn't touched it for the near second half of its existence, and I'm fairly confident I was looking at what had happened over its life time to that point.

I suppose I really should investigate the bottom of my 80 year old (plus!) tanks!

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27 minutes ago, alan_fincher said:

I suppose I really should investigate the bottom of my 80 year old (plus!) tanks!

 

This thread has got me thinking the same!

I do have to drain water periodically from our central heating oil tank at home, so I really should expect to have to do it on the boat as well.

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4 hours ago, Boater Sam said:

What engine? Some are more tolerant of bad fuel. 

But that looks to be all water and rust. Definitely dump it.

The fuel or the boat? 😊

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I took the trouble to investigate the bottom of our 20 year old shared boat three years ago. I hoovered  the bottom of the tank with a Pela pump and took out about three gallons of fluid. I let the fluid settle and then syphoned off the good diesel. Ultimately I was left with two pints of rubbish. At the bottom of the rubbish was lots of rust particles and other detritus. There was then a layer of water, maybe a pint of water or so followed by diesel that I couldn't separate out safely. 

 

The water looked like the OP's photo. Cloudy and horrible. I got rid of it by chucking it on the barbeque after we'd cooked the food.

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DIY fuel polishing can be carried out by baling out the fuel from your tank into jars and left to stand for a few days or more to allow for the separation to take place.. Muck and rust at the very bottom then water and on the top pure clean diesel which can be decanted and stored ready to pour back into the tank when the polishing process is completed. If you only have one little Shippams fish paste jar then this process could take quite a long time, a very long time, even years!!  But it is very theroputick and will afford you much excercise and plenty patience for the future,

  • Haha 1

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