Advice for Diesel Tank(s)

[Cheechako]

My experience doesn't bode well for tanks under the floor. SS failed. Aluminum failed in both tanks. Plastic is the way to go. There are premade plastic tanks available which are inexpensive. Maybe you can find a size that is close enough. Does a few gallons either way really matter? Or maybe two to fit in one space.
I see no issues with replacing the one water tank with fuel.

50 gallon, $360
https://www.westmarine.com/buy/moell...IaAqyDEALw_wcB

[SpaceRnglr]

I can't find any pre-made plastic tanks that fit this space. Ronco has a tank that is close to the size of my 4 water tanks, but it is too wide. The height of the tanks is only 26cm maximum and they all taper with the shape of the hull...

I also can't find any plastic fabrication shops in Singapore. Custom plastic tanks are already expensive, but add in freight to Asia they would be crazy. I honestly think I could get a titanium tank made in China cheaper than a plastic one from the USA. I am still looking into the tank problem, but in the meantime putting new tanks under the berths is looking better and better...

[Cadence]

You can get a plastic tank in about any shape you want, inexpensive. Pull the old diesel tank and can it. It may pay to go with your option 3 and replace the other tank at the same time. Why dick with getting years of sediment out?

[Lodesman]

Originally Posted by SpaceRnglr

Same problem with Loadesman's advice, it is very difficult to get fuel lines from the smaller tank back to the engine. That is why I was thinking just a simple connection from the smaller tank to the bigger one would work best.

Isn't there space to starboard of the diesel tank (#1)?

Originally Posted by SpaceRnglr

Argh - why is it that all boat project start as a "let me just have a peak under the diesel tank" and now have me contemplating having 3 new tanks made, changing every diesel fitting on the boat, changing all the low pressure water system, reinstalling the hot water heater, and replacing all of the toilet piping...

LOL, isn't that always the way...

[SpaceRnglr]

Originally Posted by Lodesman

Isn't there space to starboard of the diesel tank (#1)?

Sure is, plenty of space for valves and probably the pump. The problem is getting from that side of the tank to the engine requires a very long hose run around the back of the head and drilling through bulkheads I would rather not drill through....

[Capt Gill]

Originally Posted by Cadence

You can get a plastic tank in about any shape you want, inexpensive. Pull the old diesel tank and can it. It may pay to go with your option 3 and replace the other tank at the same time. Why dick with getting years of sediment out?

"You can get a plastic tank in about any shape you want, inexpensive."
Would you provide a link as to where ?

[Mike Banks]

Turtle of dart has the right idea using a plastic jerry-can as a fuel holder--but the container has to be firmly wedged between plywood compartments lined with marine carpet--so that there is no movement but it is still easy to remove them. A rack of four of these containers holds 100 litres--and takes up comparatively little space if mounted t-athwartship. or if in a cat, one rack in each hull mounted bow to stern.

The beauty of such a system with modified caps to the plummet hoses to equalise and remove fuel, is that the four tanks (or five) are similar to a baffled tank, easily removed for cleaning, and empty tanks can be dropped into a dinghy and rowed ashore to be filled at any service station if no marine bowsered fuel supply is handy.

A similar arrangement can be used for freshwater storage--with the same advantages of being able to be removed for cleaning, or for filling from stream after being rowed ashore in a dinghy. When visiting remote places one has to think of such situations in advance. When buying the water and diesel tanks--make sure to buy the ones with two outlets. It makes filling them easier when in place in the vessel. Spilled water is just a nuisance--spilled fuel is a bit of a disaster.

[Terra Nova]

Plastic tanks become permeated and stink up the boat.

[Lodesman]

Originally Posted by SpaceRnglr

Sure is, plenty of space for valves and probably the pump. The problem is getting from that side of the tank to the engine requires a very long hose run around the back of the head and drilling through bulkheads I would rather not drill through....

Fair enough, but any obstacle can be overcome. The main tank can be made shorter, or have a cut-out for the hoses to pass through (much like the current cut-out only through to the other side.

A simpler plan, would be to connect the second tank to the first at the top and bottom (hoses). It would fill straight from the main tank and vent through it. If you wanted to use that second tank as a reserve tank, then a shut-off valve on the bottom hose would accomplish that (just open it when you're filling the tanks).

[Cadence]

Originally Posted by Capt Gill

"You can get a plastic tank in about any shape you want, inexpensive."
Would you provide a link as to where ?

Jack, I wish I could remember. It has been awhile. I would suggest a copy of National Fisherman or Boats and Harbors if you can't find a supplier online.

[Lodesman]

Originally Posted by Capt Gill

"You can get a plastic tank in about any shape you want, inexpensive."
Would you provide a link as to where ?

Could try here: https://www.regal-plastics.com/custo...astic-welding/

[dcapn88]

I have an older sloop with a 54 gal. welded aluminum tank that was leaking diesel into the bilge. I removed all the fuel, cut a 10" inspection hole in the forward section (deepest w'pickup tube),(and had a sealing plate & gasket made). I then cleaned the deepest section, (including removing about 2 pounds of crud). After a final swab of acetone (watch out for the fumes) I let it air-dry overnight then coated all the welded seams in that section of the tank with surfboard laminating resin (two coats).
4 months and many sailings later it seems to be working. I now only keep about 15 gallons in it, in case I have to do the job again.