diesel fuel tank

[Ray Perry]

I have a diesel fuel tank as part of the keel. Because of rust starting to form I want to decommission the tank. I will remove the diesel and replace this with sump oil. I would like to reduce the volume (250 Lt) as much as possible before filling with oil. Would two pack foam be suitable? If not any other suggestions.
Any advice greatly appreciated.

[model 10]

It sure is hard to imagine why you need an oill tank for spare engine oil over about 5 gal. You must have a Perkins. 2 part foam will not work unless you cover it with lots of epoxy and cloth. How on earth would you get inside the tank to do the lay-up?
How about concrete?

[Bohemian17]

Here is a keel diesel tank being replaced on my endeavour 42 talk about a pain in the rear. At least this one will last a long time . I am doing it myself . Also included a picture of the old one before removal. Endeavour did a shoddy job at best.

[Ray Perry]

Thanks for the reply. The diesel tank is a section of the keel. When built a polyurethane coating was flow coated over the interior. There are only four holes:- (a) 12mm vent (b) 38mm filler (c) 8mm outlet (d) 12mm drain. I have just started to get very small amounts of rust in my filters and this is after 30 years of usage. I want to remove the diesel and replace the diesel with sump oil to prevent further deterioration. I want to reduce the volume as much as possible so that I am not carrying around an additional 250kg (approx) of oil. I have installed new diesel tanks. I can pour the foam in small mixes through the 38mm filler. I have had conflicting advice about using foam. Some say that the oil will not affect the foam and others say that it will. There has to be another product that is not destroyed by the sump oil and would be able to be used as a filler e.g. table tennis balls etc. There is absolutely no need to cut a large hole in the tank to achieve the results that I am trying to do.

[SoloBob]

Sand might be an option, if your just simply looking for a volume filler.

It would " pour " right through the filler neck.

[Ray Perry]

Thanks SoloBob,
I am trying to reduce the weight not increase it. My steel H36 is heavy enough as is. Your idea has merit but I am sure there is a product that is lighter. For every kilo of your boats weight you have to push aside a kilo of water.

[Bohemian17]

Sounds like the tank they flow coated has been compromised . Thus rusting. Is the boat steel or just the tank. ??

[Bohemian17]

Sorry just read the post above. The more weight down low the better the ride and less heel typically. If you go with foam use theb4 pound pour foam it has much more integrity and closed cell characteristics. I would fill her up tight and forget the lube oil idea personally.