Fuel tank crossover

siencyn

siencyn

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Hullo as forum has been brilliant in the past handling obscure nautical queries and is the font of all sea going knowledge, does anyone know how to transfer fuel from one tank to another on an Aquastar 38 with twin fuel tanks? It seems illogical that an engine could break down despite having a full tank but you can’t use the other good engine as it has an empty tank?
thanks.
 
siencyn said:
Hullo as forum has been brilliant in the past handling obscure nautical queries and is the font of all sea going knowledge, does anyone know how to transfer fuel from one tank to another on an Aquastar 38 with twin fuel tanks? It seems illogical that an engine could break down despite having a full tank but you can’t use the other good engine as it has an empty tank?
thanks.
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Do you have a diagram of the current set up?
 
Perhaps it is logical to have two completely separate propulsion systems so that if one breaks down you can continue on the other. Consider what would happen if the engine breakdown were caused by contaminated fuel: sending that fuel to the other engine would end up stopping it too.
 
Thanks for your comment and I totally agree & see that logic. However, shouldn’t it be optional? You move fuel when you want to? Why shouldn’t you be able to switch tanks if contamination is an issue? At the moment my port engine runs off the port tank. Stb to Stb Tank. They both are filled separately.I’m hoping there’s some flexibility engineered here that I don’t know about?
 
I'm hopeless at CAD, so I won't try to draw anything, but I assume we're talking about significant amounts of fuel, so a pump will be necessary. I've no pretensions to expertise, so others will judge whether this will work, but my first thought would be to tap into the fuel take-off from each tank and go to a T valve with a line to the input and output sides of the pump. To pump from tank 1 to tank 2, set valve 1 to input and valve 2 to output, and vice versa. A bit of care would be needed to make sure the valves are set correctly, but that would be a hellava lot cheaper than a more sophisticated system that does the thinking for you
 
Great idea! Many thanks for taking the time. I was hoping someone knew if there was already a system on Aquastars unknown to me but failing that your thoughts are most welcome.
thanks again.
 
I don't know anything about Aquastars, but my boat has twin 250 litre tanks. Each tank has a shut- off cock feeding into the crossover pipe, and the supply to engine via filters is from the crossover pipe. Thus I can select which tank is in use. (I also have to select which tank the excess fuel returns to). If your setup had each engine supplied from the crossover pipe, with a shut-off cock between the two, you could choose to supply each engine from its own tank, or from either tank.
In practice, I seldom transfer fuel from one tank to the other, and don't have a pump for doing so, but remember that you can do it by directing the excess fuel flow. I have also transferred fuel, using a dinghy pump, by pressurising a tank (blocking the breather), and using the cocks on the crossover pipe.
It would seem very strange to have a full tank of fuel, and to be unable to use it.
 
Thanks so much NormanS. Thats exactly what I thought should be on mine. However, it appears the fuel from each tank goes straight, via the filters to each engine. Putting in a common crossover should be that hard should it? I think I’ll try that. So grateful for your comments!
 
siencyn said:
Thanks so much NormanS. Thats exactly what I thought should be on mine. However, it appears the fuel from each tank goes straight, via the filters to each engine. Putting in a common crossover should be that hard should it? I think I’ll try that. So grateful for your comments!
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That's how I repiped mine. A ball valve on each tank, a pipe between them and a Tee in the middle to the filter. My tanks were tall and narrow so gravity would always move enough fuel to keep the engine running for some time.
 
What would be the best way for me to rig mne? One engine, 2 deckfills, 2 racor filters, 2 tanks, one tank higher than the other.. Any ideas?
 
vic008 said:
What would be the best way for me to rig mne? One engine, 2 deckfills, 2 racor filters, 2 tanks, one tank higher than the other.. Any ideas?
Click to expand...
What do you want to achieve? Presumably both tanks have cocks, so you can select the one you want to use.
 
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