Fuel Distribution

[AJH]

Just purchased a 1989 54ft Californian motor yacht. Comes equiped with 3 fuel tanks. Two 85 gallon saddle tanks and one 330 gallon main tank. The attached photo shows the current fuel distribution via three way valves. With this setup fuel is only being used from the saddle tanks. Question is what is the setup to draw from the main tank? Also is it possible to only draw fuel from the main tank bypassing the saddle tanks?

 

[luna]

To me, with all 4 valves pointing (by way of the short, blunt arrowhead on the opposite side of the pivot shaft than that of the turning handle) to the right, both engines have their fuel supplied from and returned to the Starboard tank. That would be pointing the 3 o'clock position.
If you were to turn the arrowheads to point to the 12 o'clock position, both engines would source and return fuel to the Aft tank. If that's the 330 gallon tank great.
Likewise, if the arrowhead both pointed to 9 O'clock, you guessed it, the port tank is in use.

A few notes:

- Arrowheads at 6 O'clock, if possible, with turn the fuel flow off, which is a good thing if you don't intend to use the boat for a couple of weeks or more.

-If an engine is using fuel from one tank, like the sign says, return the fuel to the same tank, unless you like to run out of or spill fuel, whichever occurs first.

-If the boat has a fuel polishing system one way to use these 3 tanks effectively is to have the engines only use fuel from the Port and Stbd. tanks. All new fuel purchased goes only into the Aft tank. As the P & S tank are drawn down, pump fuel from the Aft tank through the polishing system into the P and then S tanks refilling then. This way you know you are using fuel that has been filtered at least once before the rest of the onboard fuel filtration system is used.