B28 Diesel tank question

[Yannis]

I decided to clean my diesel tank. It is made of f/g with 3 riveted SS buffers that only leave an inch or so in the bottom for the diesel to flow.
As you can see in the first photo, the only access hole (initially) was the aftmost one, the one which is smaller than the rest. So to access the remaining 3 compartments we opened 3 more access holes.







After cleaning as best I could with my pressure pistol, the situation in the 4 compartments is shown in the following 4 pics (from aft to fwd):










The water pistol cannot flex to reach the "ceiling" of the tank; the condition of the gelcoat(?) on the ceiling of one compartment is shown below:




The condition of the ceiling of the 3 compartments opened is shown in the extracted oval pieces, below:





As you can see, whatever the inner coating of the tank is (it looks like gelcoat that has been "cured" by time and diesel), it has flaked. With the pressure applied, all flakes that were either already broken off, as well as those that were ready to break, they were all cleaned and disposed off with the hand pump. There are some remnants that I plan to remove with the hoover so that in the end the tank will be clean and there will not be any loose flakes EXCEPT for the ceiling ones.

Question: What do I do next? Is the tank OK to fill up once it's clean and dry? Shall I bother about the ceiling? The only way to clean it is with the hoover's brush (the one for the furniture). There is a fine mesh at the diesel intake's end that would stop all debris from going through; anyway my filters never showed any trace of flakes so far.

Thank you in advance for your eventual input.

[Kevin]

Yannis,
I am not a FG expert but I am thinking it is probably fine. When I converted gas to diesel I had a polishing company come and pump out the gas. They poured in some diesel and ran their machine with the flexible wand for a while. Launched the boat and filled it up and have not looked back since. Keep the filters healthy. If you don't see junk, algae or water in the bowl you are good to go. Flakes would likely never make it past the screen. If you do see anything just drain them and change out filters regularly. Hell, I cut a hole in my tank by the pick-up for a high speed diesel nozzle fill since the gunwhale fill always burped. Never did recover the piece that fell in. That was 7 years ago.

[Yannis]

Thanks Kevin.

I didn't know there were different speeds in diesel fill-ups !
By the way, there were algae in my filters that's why I opened the tank. I don't know how they can be exterminated permanently; does a thorough cleaning like this suffice? We'll see.

[CaptPatrick]

Yannis,

Algae in diesel fuel can be eliminated and managed by using an algaecide such as Hammonds Biobor JF...

The first treatment is called a shock treatment is is a heavy dose to break up algae clinging to the tank walls. You'll go through several filters during the initial treatment. Then adding the Biobor in smaller amounts, usually during refueling, keep the algae in check. You might want to contract a fuel polishing company for the initial treatment and filtering, if there's one available to you.

Hammonds Biobor JF (last item on webpage)

[Yannis]

Thank you Captain.

Shall I assume that the first shock treatment that you suggest is not needed for me, now that the tank is pressure clean, the filters are soap cleaned and the lines are empty?