Fuel tanks equalizing

[ofer]

I have four 200 gal tanks all same dimension and are installed level.
a supply manifold and a valve for each tank and a return manifold with a valve for each.
i normally run from and to the same tank one valve open on each manifold.
Any reason not to open all four valves and let tanks equalize and continue to run that way.

 

[SeaDogAK]

I wouldn’t.

I’m no expert but I’d be afraid that, if the back flow is a little uneven, you’ll overflow one of your tanks.

 

[C lectric]

Bluemoon has a point.

However, my boat has a list from fuel imbalance. I do what you propose.
I have a single engine and two tanks of about 130G each.
There is a single feed line from both tanks, dual return lines from a valved mfld. with one line to each tank.

The ONLY time I ever had an overflow was when I allowed my self to be rushed to leave a fuel dock. I always shut off one of the tanks engine feed valves so they cannot cross feed when refueling. That way I know what went into each tank.

This time I forgot to open the valve , took off and 1/2 hr later the light went on and I roared out and checked the vent and it was spitting fuel.

The instant I opened the forgotten valve the fuel loss quit.

It took 25 - 30 yrs to make that error. I have not allowed myself to be rushed since no matter who wants what. I don't dawdle but I don't want that to happen again.

If the return mfld has valves you can direct return fuel to faster feeding [level dropping] tanks.

Just keep a close eye on the tanks as your boat may react differently. You don't want my experience.

 

[mvweebles]

With your tanks balanced, trim your boat woth movable ballast (lead ingots - check under your side decks for existing) so it's level. You can then run your tanks ganged together if you want.

Issue is that over time as gear added, boat gets out of trim. Fuel meanders to low side and makes matters worse.

Good luck.

Peter

 

[O C Diver]

I took a different approach when doing the refit on my boat. One of my water tanks and the holding tank are mounted to port. As a result, I use fuel to level the boat relative to the other 2 tanks.

Also, I'm paranoid about getting bad fuel (it's happened). So I only add fuel to my port tank, transfer / polish it to the starboard tank, and feed the generator and main engine from that tank. Since the tanks each hold over 300 gallons and I usually burn about 15 gallons a day, there's only a slight imbalance after a day of cruising. It's a simple matter of transferring some fuel each morning when doing the prestart engine room checks. An added benefit is all the fuel gets moved to the starboard tank when I fuel the port tank, meaning old fuel isn't theoretically sitting in one tank.

Ted

 

[AusCan]

In theory, having all the tanks equalized should keep the boat level, although in real life this doesn't always happen. As mvweebles mentioned, if something else causes causes the boat to list then the fuel will flow to the lowest tank making the list worse.

The initial list may be caused by uneven water tanks, people sitting on one side of the boat, equipment storage, or even just a strong wind on the beam.

I prefer to keep my fuel & water tanks isolated, and just swap (either fuel or water tanks when a list starts to develop.