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Old 12-04-2013, 12:00   #1
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Water tank converted to fuel tank

How do you convert a SS water tank to a fuel tank on a 1990 Jeanneau? Any help would be appreciated.

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Old 12-04-2013, 17:15   #2
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Re: Water tank converted to fuel tank

you need to somehow fabricate a vent , and be able to install a sending unit and fuel pump combo..

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Old 12-04-2013, 17:21   #3
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Re: Water tank converted to fuel tank

Ahh and ya need a return line also ! LOL
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Old 12-04-2013, 17:53   #4
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Re: Water tank converted to fuel tank

Step One: Remove the water. (Sorry, sometimes I'm a wise ass)

Is the tank clean inside? Now is the time to clean it.

Presumably the tank is already vented and the fuel pump is on the engine.

Don't forget to change the vent and fill hoses to ones appropriate for fuel. Change the deck fill to one marked "Diesel" or "Gas" as well.
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Old 12-04-2013, 17:59   #5
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Re: Water tank converted to fuel tank

Check photo below of my tanks. Water tank is lower in photo, fuel is above. Both tanks have access covers (opened in photos). My fuel tanks has the following connections:
  1. Fill pipe
  2. vent pipe
  3. main engine pickup with shutoff
  4. generator pickup with shutoff
  5. main engine return line
  6. generator return line
Any existing hose (e.g. fill pipe) needs to be fuel grade.
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Old 12-04-2013, 18:20   #6
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Re: Water tank converted to fuel tank

Now is the time for a cleanout port.
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Old 15-04-2013, 11:55   #7
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Re: Water tank converted to fuel tank

Did it in 2000 to our center 85 gallon aluminum water tank - has worked for 13 years and many hundreds of gallons of diesel

We did have a 6" inspection plate in the top - if you don't have at least that big an opening - you will need it!

- remove inspection plate
- drilled and installed vent fitting into tank top
- drilled and installed vent outlet on side hull in appropriate location
- ran vent line from tank to hull and connected both ends (this was difficult and time consuming)
- tested vent connection with compressed air
- adapt existing fill neck in tank to fuel line and connect fill hose/line
- drilled fill hole in deck and installed fitting
- ran fill line to appropriate deck space and connected (difficult and time consuming)
- drill and install return port into new tank
- block return port at tank
- tested fill line by running water into tank
- installed inspection plate
- used fill line to overfill with water
- verified vent worked and tank did not leak at return port, vent outlet, fill neck

- pump all water out
- using towels / rags / sponges - sop up all the water (we could not reach the edges of our tank but it did have a nice sump)
- used a small electric 1500 watt heater to blow warm dry air into tank for 24 hours
- poured a quart of alcohol in and sloshed it around
- mopped up all the alcohol
- CAREFULLY inspect tank, by eye and by touch, for metal shavings from drilling
- let air dry for a day
- used 1500 watt heater to air dry for another day
- using appropriate adapter - connect old water pickup line to fuel line
- installed 2nd set of valves in fuel manifold so that intake and return can come from/go to either tank and either fuel filter
- run fuel line from fuel pickup at tank to diesel filter manifold at appropriate valve
- run return line from manifold to new tank
- connect to return tap on tank
- remove inspection plate
- put a gallon of fuel in tank and tested using lift pump and lined up fuel manifold to return fuel to new tank and then to old tank
- put in another gallon of fuel and tested with diesel running
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Old 15-04-2013, 12:56   #8
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Re: Water tank converted to fuel tank

I"ve seen this done many times in my business. Fuel tanks are often baffled and water tanks are not. One of the things that is often over looked is the water out put line. Many times this is a lot different configuration than a fuel pick up line. Water pumps can withstand air in the lines as the level gets low and water is sloshed around in a bumpy sea. So the water tank out put is usually just located somewhere close to the bottom where it's convenient. Fuel pick up lines are a different matter. These usually reach down very close to the bottom of the tank at it's lowest possible point helping reduce air ingress when the fuel is low. If this is the case on your water tank you'll have to be careful not to let the tank level get too low where you can start sucking air at the worst time. This of course means reduced capacity that should be factored in when considering how much fuel is really reliably useable.
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Old 15-04-2013, 17:35   #9
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Re: Water tank converted to fuel tank


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fuel, water

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