convert water tank to fuel tank?

[Cpt Mark]

Question for those cruisers out there cruising or have been.

I'm going cruising. Getting down to the last few projects. I have a watermaker, 16gph capacity. I have 2 diesel engines that burn about .75-1 gph.

2 water tanks 70 gallons each. Heads are freshwater plumbed.

1 fuel tank 55 gallons. Motoring on one engine is about 4.5 knots conservatively so my range is about 250 nm. Not much.

My hardtop bimini is 10'x10' with a lip all around so I can easily catch rain water.

I'm wondering if it might be beneficial to to convert one water tank into a fuel tank? I can make water but not fuel.

[HopCar]

What is the water tank made of?

[Cpt Mark]

Aluminum

[HopCar]

Aluminum water tanks develop a strange gel on the sides. If you can get access to the inside to clean it, I don’t see why you couldn’t convert it to fuel. Of course when you see the crap inside you might want to change your water tank to plastic.

[NorthCoastJoe]

I did it and no problem. Just make sure you make the wording on the fill FUEL. It would not be a good thing if someone filled your fuel tank with water.

[Pizzazz]

I am considering the same conversion, I have three 800L / 211 gallon tanks, stainless, the outer ones are fuel and the inner one is water. I will convert the middle one to diesel as well. The question is, if I ever want to switch back to water, is there a practical and reliable way to clean diesel from a stainless steel tank to make it potable water ready?