Cleaning a fibreglass diesel tank?

[neil1967]

Hi, I am cleaning the (500 litre) fibreglass diesel tank of my 1987 Oyster 406. I have already pumped out the fuel, through a Racor with a 2 micron filter. The tank is on the top of the keel and is an integral part of the boat. The good news is that there is a 10" inspection hatch in the top, so access is good, but the bad news is that the tank, by its very nature is an odd shape, with various curves, nooks and crannies. After 37 years of use there is quite a lot of sticky tar-like residue in the bottom of the tank (a combination of black, brown and white), most of which I have removed simply by scrapping, but I would be grateful for advice on how to remove the remainder, which is generally in the hard to access areas. Ideally I would like to use some form of liquid to dissolve the remaining deposits that I can then simply suck out. I would like to avoid petrol, simply from the safety aspect. Could I use Gunk, or any of the myriad of other industrial engine degreasers, without harming the fibreglass, or is there another way? Any advice appreciated, but no need to go into a discussion about the why's and wherefor's of the diesel bug, this is just about cleaning of the residue.

 

[Blue Seas]

Hi, I am cleaning the (500 litre) fibreglass diesel tank of my 1987 Oyster 406. I have already pumped out the fuel, through a Racor with a 2 micron filter. The tank is on the top of the keel and is an integral part of the boat. The good news is that there is a 10" inspection hatch in the top, so access is good, but the bad news is that the tank, by its very nature is an odd shape, with various curves, nooks and crannies. After 37 years of use there is quite a lot of sticky tar-like residue in the bottom of the tank (a combination of black, brown and white), most of which I have removed simply by scrapping, but I would be grateful for advice on how to remove the remainder, which is generally in the hard to access areas. Ideally I would like to use some form of liquid to dissolve the remaining deposits that I can then simply suck out. I would like to avoid petrol, simply from the safety aspect. Could I use Gunk, or any of the myriad of other industrial engine degreasers, without harming the fibreglass, or is there another way? Any advice appreciated, but no need to go into a discussion about the why's and wherefor's of the diesel bug, this is just about cleaning of the residue.

The secret is to keep it as 'concentrated' as you can for as long as you can - the more concentrate that you can remove the less faff and disposal issues you will have. We use a wet & dry hoover plus cheap industrial blue roll to get as much out as poss - and put the liquid from the hoover into 25ltr plastic drums from the local farmers supplies store. We then use concentrated washing up liquid with hot/warm water and leave overnight if poss to emulsify - again staying concentrated if possible. Some marinas and most council sites with then take the concentrated oil waste - often you can tip it in their tank and re-use the containers.

 

[LiftyK]

I have used Screwfix No Nonsense degreaser on occasion. It worked well. Use a soaked sponge on a stick to reach the awkward parts.

 

[Sandy]

Sounds like another bl00dy awful bit of boat design.

Can you get to all the nooks and crannies with a steam cleaner? A big industrial one, not some piddly thing for removing wall paper.

 

[Refueler]

1. I really do not like introducing any liquid that may leave something that cannot be burnt in the engine later.
2. Kerosine is a good 'solvent'to loosen / dissolve tar etc ... still volatile of course but less than petrol.
3. Clean diesel with an enzyme added and then vigorously agitated - then left in tank can lift some of it.

Engine degreasers ? Maybe - but often they have aggressive solvents ... so good rinsing out would be needed. And unlikely you can have any passing through engine after.

If access to a reasonable Steam Cleaner - then that would be my non-fuel based method ... making sure after that all water / mix is sucked out.

 

[neil1967]

1. I really do not like introducing any liquid that may leave something that cannot be burnt in the engine later.
2. Kerosine is a good 'solvent'to loosen / dissolve tar etc ... still volatile of course but less than petrol.
3. Clean diesel with an enzyme added and then vigorously agitated - then left in tank can lift some of it.

Engine degreasers ? Maybe - but often they have aggressive solvents ... so good rinsing out would be needed. And unlikely you can have any passing through engine after.

If access to a reasonable Steam Cleaner - then that would be my non-fuel based method ... making sure after that all water / mix is sucked out.

Thank you. I think physical extraction of as much as possible, followed by a kerosine wash and soak is probably the way to go.

As a separate question, how far above the bottom of the tank do you think the end of the fuel pick up should be? 2-3 cm?