Fuel selector manifold: is there an off position?

[cwillemssen]

I am hoping someone in this group might have an answer to a perplexing situation regarding the fuel tank supply/return arrangement on my 1989 Hatteras 70' CPMY, which is relatively new to me.

This build came from factory with a custom fuel tank arrangement that includes the standard 4 fuel tanks (fwd, fwd mid, aft mid, aft) plus 2 additional tanks beneath couple of berths (port berth, aft berth). Allows for about 300 gals of extra fuel.

Hatteras supplied what I assume are the standard tank supply/return selector valves (4 position for the standard 4 fuel tanks--see pic 1). They also then plumbed the additional tanks to individual ball valves (see pics 2 and 3), which ultimately tee into the main supply or return lines of each engine. That sounds sensible, but it does leave a seemingly simple question:

1. How do I arrange the manifold selector options to supply and return from one of the additional tanks? Seems simple: just open one of the additional tank supply and return ball valves. The underlying question is, in the situation of desiring to use one of the additional tanks--what do I do with the standard 4 position selector valve? Does it have a no-flow condition if it is positioned "in between" one of the 4 tank positions?

Little additional note: condition of fuel currently residing in the additional tanks is unknown. Prior owner appears not to have used the additional tanks regularly, thus I want to be very careful and intentional of how I pull from the additional tanks. This will involve a small polishing system (pump/filter/separator) to circulate fuel of each additional tank until i decide if it is usable or needs to be disposed of. Once i feel good about the fuel condition, i will use that polishing pump to transfer fuel from one of the additional tanks to one of the standard tanks. That way i can always run the main engines off one of the standard 4 tanks.

Thanks in advance for your thoughts.

 

[rwaldrop13]

The only suggestion I have is supply valves before the manifold. I had to hand-trace my fuel line plumbing on Pau Hana, to determine what the correct valve positions should be.

 

[Captain Ralph]

Hopefully there are complete tank shut-off valves on the tank-top supply outlets.

 

[CGHOST4]

On my auxiliary tank which has a similar arrangement to yours, there is another set of valves which turn off the supply and return lines to my forward tank. So when I use the auxiliary tank I place the main selector valves in the forward tank position which is now actually turned off. I think you will find another set of valves on one of your tanks. I hope this helps.


Caesars Ghost
1980 58YF #472

 

[cwillemssen]

Thanks everyone for the input! Excellent advice on tank valves.

I did do some hunting around, unfortunately couldn't find any shutoff valves at tanks, so I have decided to add in a couple isolation ball valves that will help me direct fuel from the accessory tanks to the proper locations (either recirculating for polishing OR into one of the 4 main returns for transferring).

As has usually been the case, the forum has helped out a bunch.