How to clean fuel tank

[Lazysloth]

Hello
Bit of a long story here but please bear with.
We have a boat which had a diesel engine in, we have swapped this out for a petrol engine. The fuel tank had the diesel pumped out and fresh petrol put in and then pumped out until it ran clean (please see first photo) we the topped her up with more petrol and took her for a sea trial where she promptly cut out and would not start.
Suspecting a fuel flow issue we checked the filter to see it completely clogged with gunk. (I'm not sure where this has come from or how it was missed when we previously emptied the tank..

Is there any way of flushing the tank properly to Clean it out as I have no idea how much of this sluge is in the tank.
There is no inspection hatch and I'm unable to the get the tank out the boat of the sender out of the tank to have a look inside. Any help or ideas would be greatly appreciated.
Thanks

 

[AntarcticPilot]

Without an inspection hatch, I think you've got a problem. There are companies that will clean fuel tanks, but I think they require better access than a filler can provide - but I'd approach them first. I don't know where you're based but Google is your friend!

The sludge looks like "diesel bug" - that is, a microbial contamination of the fuel; it can live off diesel oil and small amounts of water. It's a well-known problem. There are chemical treatments (e.g. Grotamar, Marine 16) some of which break the "bug" down, but a) I don't know if they'd work in petrol and b) you may have too much contamination!

 

[Lazysloth]

Without an inspection hatch, I think you've got a problem. There are companies that will clean fuel tanks, but I think they require better access than a filler can provide - but I'd approach them first. I don't know where you're based but Google is your friend!

The sludge looks like "diesel bug" - that is, a microbial contamination of the fuel; it can live off diesel oil and small amounts of water. It's a well-known problem. There are chemical treatments (e.g. Grotamar, Marine 16) some of which break the "bug" down, but a) I don't know if they'd work in petrol and b) you may have too much contamination!

Hey,
Thanks for the reply, I'll follow your advice and see if I can find a company and also research whether marine 16 will work in petrol.
Thank you

 

[wallacebob]

If you can’t remove the tank to clean every surface and inspect, then the tank will have to be brimmed several times, agitated, drained. Costly! Even then….
Google cleaning car tanks. If it’s steel, it’s probably corroded anyway. Get a petrol outboard tank.

 

[Refueler]

Most additives will work in gasoline ... gasoline is only steps up the fractionation of crude.

What gasoline will do is act like a solvent and dilute the effect of the additive.

The problem now that gasoline has been put in the tank - means risk if wanting to cut an inspection / access hatch. Personally I would empty out the fuel. Then fill tank overflowing with water .... to push out gasoline vapours ...

While STILL full of water - then cut a hatch. A plate and gasket can be easily made up to fit.

Once hatch is made ... pump out the water ... then get a high detergent oil dispersant cleaner in there ....... as its obvious that the initial use of gasoline was only dislodging it - not actually dissolving or cleaning. GUNK ... is a brand ... as is Gamlin etc - there are many other engine external surface cleaners ... many of which have enzyme base - the required base to deal with this problem.

Its not an easy one ....

You may decide to just cut out the tank and replace with a new plastic tank ... such as Tektanks or similar.

 

[Dellquay13]

Most additives will work in gasoline ... gasoline is only steps up the fractionation of crude.

What gasoline will do is act like a solvent and dilute the effect of the additive.

The problem now that gasoline has been put in the tank - means risk if wanting to cut an inspection / access hatch. Personally I would empty out the fuel. Then fill tank overflowing with water .... to push out gasoline vapours ...

While STILL full of water - then cut a hatch. A plate and gasket can be easily made up to fit.

Once hatch is made ... pump out the water ... then get a high detergent oil dispersant cleaner in there ....... as its obvious that the initial use of gasoline was only dislodging it - not actually dissolving or cleaning. GUNK ... is a brand ... as is Gamlin etc - there are many other engine external surface cleaners ... many of which have enzyme base - the required base to deal with this problem.

Its not an easy one ....

You may decide to just cut out the tank and replace with a new plastic tank ... such as Tektanks or similar.

A good point about the risks from empty petrol tanks. They are highly flammable and explosive when full of air and a bit of petrol vapour. Displace the air/vapour mix before getting your angle grinder out

 

[AntarcticPilot]

I should, perhaps, have mentioned that when I had similar trouble (with diesel in the tank, not petrol), cleaning the tank ended up removing the last bit of rust that was keeping fuel in the tank - I ended up having to replace the tank.

 

[burgundyben]

I don't think you'll resolve this without getting inside the tank.

 

[vyv_cox]

I have thoroughly cleaned three diesel tanks but each was removed from the boat(s) first. Scrubbing, detergent, hot water followed by thorough drying.

 

[Refueler]

First I'm trying to get head round replacing a Diesel engine with a Petrol .... with increased running costs ???

I assume looking at the photos and seeing VP filter - this is a motor boat with a reasonable sized engine ? Likely an outboard tank is not large enough ??

Unfortunately - gasoline once contaminated is not so easy to filter and clean as Diesel fuel - as it is more like a solvent. I hope the amount of fuel in that tank is not a 'wallet busting' amount ?

 

[Lazysloth]

If you can’t remove the tank to clean every surface and inspect, then the tank will have to be brimmed several times, agitated, drained. Costly! Even then….
Google cleaning car tanks. If it’s steel, it’s probably corroded anyway. Get a petrol outboard tank.

This is a really good idea I did not think of a outboard tank. The boats tank is 215L I will see if I can find anything close to that

 

[Lazysloth]

Most additives will work in gasoline ... gasoline is only steps up the fractionation of crude.

What gasoline will do is act like a solvent and dilute the effect of the additive.

The problem now that gasoline has been put in the tank - means risk if wanting to cut an inspection / access hatch. Personally I would empty out the fuel. Then fill tank overflowing with water .... to push out gasoline vapours ...

While STILL full of water - then cut a hatch. A plate and gasket can be easily made up to fit.

Once hatch is made ... pump out the water ... then get a high detergent oil dispersant cleaner in there ....... as its obvious that the initial use of gasoline was only dislodging it - not actually dissolving or cleaning. GUNK ... is a brand ... as is Gamlin etc - there are many other engine external surface cleaners ... many of which have enzyme base - the required base to deal with this problem.

Its not an easy one ....

You may decide to just cut out the tank and replace with a new plastic tank ... such as Tektanks or similar.

Thank you for all the info, I think perhaps the easiest thing to do is fill it with water as you that. Empty it and then cut the tank out and replace with an outboard on if I can find one large enough. Thanks

 

[Refueler]

This is a really good idea I did not think of a outboard tank. The boats tank is 215L I will see if I can find anything close to that

215L .... I hope your failed sea trip didn't have that much in tank ??

At that sort of size ... and don't forget - a gasoline engine burns more litres per hour than a diesel for same performance ..... I think you will need to look at a flexi tank .. Tectank or similar ...

 

[Lazysloth]

First I'm trying to get head round replacing a Diesel engine with a Petrol .... with increased running costs ???

I assume looking at the photos and seeing VP filter - this is a motor boat with a reasonable sized engine ? Likely an outboard tank is not large enough ??

Unfortunately - gasoline once contaminated is not so easy to filter and clean as Diesel fuel - as it is more like a solvent. I hope the amount of fuel in that tank is not a 'wallet busting' amount ?

Yeah I know it's counter intuitive. Basically this is our first ever boat, we wanted diese due to running costs so bought the only one in our price range which had the original petrol engine replaced with a marinised diesel engine. it was only doing 5 knots when we got it and we was told it needed a new turbo. Anyway 18 months later and 5k + the engine has had a new turbo and had the top end rebuilt however still only doing 5 knots. Had 2 engineers look at it and neither could figer it out so we decided to cut our losses and replace the engine. This petrol engine was the only one we could afford after blowing so much money trying to repair the previous engine which Is why we have made the illogical step of going from diesel to petrol. I know it seems counterintuitive but I'd rather have a petrol that works than a diesel that doesnt.

It has a 5L V8 Volvo penta in. The orignal tank size is 215 but the largest outboard tank I've been able to find is 140. There is about £100 of fuel in there, in the grand scheme of things not too much.

Anyway rant over, thanks for listening haha

 

[B27]

If the tank is stainless or ali , it's probably worth saving it, otherwise maybe not.

The problem is, a lot of boat tanks don't draw fuel from the very bottom, so they allow several litres of crud and water to accumulate..
So I think you will need to cut new access to get right to the bottom.

Personally, if considering over 100 litres of fuel, then I'd consider two tanks.

Steam might be useful for cleaning? The kind of steamer sold for removing wallpaper.

 

[AntarcticPilot]

If the tank is stainless or ali , it's probably worth saving it, otherwise maybe not.

The problem is, a lot of boat tanks don't draw fuel from the very bottom, so they allow several litres of crud and water to accumulate..
So I think you will need to cut new access to get right to the bottom.

Personally, if considering over 100 litres of fuel, then I'd consider two tanks.

Steam might be useful for cleaning? The kind of steamer sold for removing wallpaper.

All the above is very true. Mild steel tanks are a) common and b) last plenty long enough (mine was over 20 years old when it rusted through and plenty of people get longer). Tanks are normally drawn from a dip tube, so a failure in a fuel line doesn't result in the tank draining into your bilges.

Commercial tank cleaning outfits indeed use steam cleaning.

 

[PetiteFleur]

Replace your tank with a plastic tank, Tektank has been mentioned, Plastimo & Osculato also make them. 120 litres was the largest I found on a quick search.

 

[fisherman]

Tek tank go to 500 lts

 

[wallacebob]

This is a really good idea I did not think of a outboard tank. The boats tank is 215L I will see if I can find anything close to that

Sorry, my misunderstanding: I assumed you’d replaced a small diesel with an outboard on a sailing boat! The engine saga sounds like a sorry tale. You have my sympathies. Is your hull clean? What type of boat?

 

[Refueler]

Sorry, my misunderstanding: I assumed you’d replaced a small diesel with an outboard on a sailing boat! The engine saga sounds like a sorry tale. You have my sympathies. Is your hull clean? What type of boat?

His photo did show a Volvo Penta filter ... a dead give away that its not an outboard !!