Poss. to overflow fuel tanks when running from one side?

Boat Guy

Boat Guy

Well-Known Member
May 15, 2013
2,289
Who knows? Could be Cali, Oahu, Florida, Annapolis
Boat Info
400 DA
Engines
CAT 3116s
On my boat, and I imagine on many others, there is a fuel selector valve. It's function is to allow you to select which diesel tank to use when operating each engine.

Though, because with diesel there is return line, and I think the return doesn't change when you change the supply, it seems possible to overflow a tank, if you're not careful, no?

In other words, if you have setup so both engines run off the port side, the stdb. engine is still going to return fuel to the stbd side, no? Then if the stbd. fuel tank was relatively full, you could potentially overflow it....Also, I guess this could be used as almost a fuel transfer option.

Am I wrong or is there some safe-guard?
 
Pretty sure that when you switch the tanks both the feed and return lines are changed together. It would be pretty dumb to do it any other way.
 
My friends overflowed a tank on their Ocean doing that. That boat wasn't equipped with sea strainers either though, so I guess it's not a great comparison.
 
Here's the diagram from the parts manual for my vessel....

400DA Fuel lines.png
 
I would have to follow the return lines from the engines, but agree the drawing does not show switched return lines. Drawing are usually correct as to how it was built though.

I think the tank would eventually overflow.
 
If your boat was ordered with the optional fuel manifold, then the fuel valves are 2-gang valves - the fuel supply is switched on the top valve; the return is switched at the same time so you cannot run one tank while returning fuel to the other one. Here is a diagram:


Screen Shot 2019-06-05 at 11.53.07 AM.png



If you don't have the optional manifolds, then you just have on-off valves as your diagram shows.
 

Attachments

  • Screen Shot 2019-06-05 at 11.53.07 AM.png
    Screen Shot 2019-06-05 at 11.53.07 AM.png
    116.8 KB · Views: 105
  • image.png
    image.png
    105.9 KB · Views: 130
A friend and fellow CSR member, had separate supply and return lines for each engine and was able to use them essentially transfer fuel from one tank to another. With that setup, yes, you can overflow a tank if you are not keeping an eye on it.
 
Are you looking at the 'gas' flow diagram? in some years, 400DA's were available with either gas or diesel. It doesn't even appear to have the return lines noted... although it appears to be showing the fuel pickup and and the fuel return fittings on the tank.
 
Perhaps it's gas fuel diagram...There isn't another in the parts manual....

Though, looking in the bilge, it does appear that both the supply and returns head to the direction of the manifold valves. So perhaps my drawing is incorrect and they both do go through the valve.
 
Not to hi-jack here... somewhat on topic:
My boat has duel tanks, but no selector manifold. What is the advantage of the fuel selectors?
 
You must log in or register to reply here.

Forum statistics

Threads
113,124
Messages
1,426,651
Members
61,037
Latest member
wojozobl
Back
Top