A27- Fuel Tank Removal & Install

[JT48348]

Bolting into top of tank worked excellent for the inspection ports and new fuel sending unit. I heartily recommend this DIY project. It's not necessary to purchase those Seabuilt inspection hatches ( which run $197 for one hatch). I put in all the hatches & sending unit, and got the tank welded for the cost of what would have been one hatch.

Tank repaired by welder and pressure tested no leaks.
Booya

[sail149]

What a really interesting study of an old tank and also the cleaning and repair.
Impressive evidence to debunk much of the algae stories. I'm sure there is some such algae in tanks with too much water but what you found is I guess what one might expect.
I'm not sure if you said any fuel products actually disolved the crud you found.
Did it disolved in diesel or was it now perminant solids? Ie would it redisolve in a fuel polishing setup?
I ask as I wonder if the tanks are semi self cleaning or polishing if the diesel is changed or used regularly?
I don't know what sort of quantity of excess fuel returns to a tank when normally running but I think it must be quite a bit......prehaps the difference in the fuel used per hour and the flow rating of the feed pump?
Is the return flow higher when the engine is using less fuel?

More importantly for you with a beautiful clean tank how will you keep it that way?
We used to use a pre filter on a sailboat years ago as we did not trust the old tank we got our 5-10 gal per year.
Our filter? We used old clean nylon stockings donated to the cause! We always saw a few flecks of dirt/ rust maybe , we has to transfer from our own 5 gal top up can. I gather you can also get official pre tank filters and most suppliers have good filtering these days. But having said that you seem to have found the crud is probably coming out of the fuel as it ages, evaporated or degrades?
The large cargo ships I know have to use 'pre-heaters' to make the 'bunker fuel' they use to make it flow at all! I expect they have plenty of crud build up! I also read about an expedition sail boat who used a small 2-5 gal header tank installed above the engine to help keep the fuel warm and extra clean with pre filters.

Your study of an old tank is great, thanks so much for posting photos and analysis . I don't think I have ever read such good information. Even if it does raise some additional questions that are all good.
Warren
Ps you have prehaps not inspired me to do the same but I will watch my filter more closly when the time comes!

[sail149]

JT
Doing some re-reading....since you are replacing the engine prehaps you don't need that fiberglass box that pushes the tank back further? Could you move the tank forward and add extra storage under the steps in the aft cabin.?

By the way one other way to have done the inspection plates might have been to use thicker plate, drilled and tapped then slip it into tank thru the rectangular hole, turn 90 deg and then use bolts fron the top thru the tank wall into the cover plate mounted on the inside. But since you decided quite correctly that just tapping the tanks for the bolts worked well then you are in good shape.
Just another idea. ( too late!)
Warren

[JT48348]

Thanks for the feedback. I like your hatch idea. That's a very clever solution to a tank with too thin walls! Very good idea.

-based on my observation there is zero chance any of that solid could have been dissolved or polished out of the system. The only way to clean the tank is by removing the solid.

- acetone seemed to clean the oily residue off the inside on the tank walls but there's nothing that would have helped the solids

-based off my research what I found in my tank is consistent with at least two other boat restorations where the owners cleaned their 30 year old tanks. I would tell someone: if you have a tank that hasn't been properly maintained for decades you probably have the same thing. There's two primary issues: fuel breaking down over time and water entering the tank.

-I've found at least two debunkings of the "condensation" myth. And I think the culprit is usually leaky deck fills for water entering the tank. Thus I installed raised deck fills to eliminate water leaking through the fill.

-how long it takes for the diesel to breakdown is a good question.

I'm going to keep my tank clean by monitoring the fuel I put in it. I'm not worrying about condensation. I may treat the fuel occasionally but not sure with what. And my goal is to not leave bulk fuel sitting for more than a year. In five years of need be, I open it up and clean again.

[JT48348]

Re:engine box

This is is a very good point. I never thought of that. The box didn't seem to have anything to do with the Nissan Ld28. And it won't matter to the new engine either.

The removal of that box would likely create an extra 12" of space. I will have to crawl in there and check.