Ever Changing listing problem, list will not go away

[Ksoulant]

I’m trying to figure out how to get rid of an ever changing list to starboard problem. I will try to explain as best as I can. First here is the model of the boat and on board systems configuration. The boat is a 1988 Jefferson Sundeck MY with twin Cat. 3208T. it has twin fuel tanks port and starboard with sight glasses that can be turned off or on. It also has centerline holding and water tanks. The batteries are directly in front of each engine, the genset is to port and the water heater is to starboard the battery for the genset is on center line. The port engine fuel return line goes to the port tank and the starboard engine return fuel line goes to the starboard fuel tank. The genset return fuel line goes to the port fuel tank. There is a fuel manifold that the port and starboard engine draw fuel from and the genset draws from it also, at the manifold the fuel lines from the tanks can be shut on or off and so can the fuel lines to the port and stb. engines and the genset. The fuel tanks also have an equalization line connecting the two tanks this line is also capable of being shut on or off.
When the fuel tanks are equally full the boat has a slight list to starboard 1-3 degrees. If I open the equalization line the starboard tank will start receiving fuel from the port tank (I’m suspecting due to the list). If the equalization line is left open the fuel in the port tank will eventually fill the starboard tank and the boat will have up to a 10 degree list. If I leave the equalization line off and run the genset in about
4-6 hours the fuel return from the genset into the port tank will fill that tank; it will equal the boat out until overflowing that tank
I am trying to figure out this problem without adding any weight to the boat does anyone have any suggestions.
Thanks.

[GordMay]

Greetings and welcome aboard the CF, Ksoulant.

That’s certainly a puzzle.

FWIW: The Fuel Return Lines MUST ALWAYS return to the tank from which the fuel was drawn.

[nigel1]

Welcome,
When your running the gen set, I assume that the fuel system is lined up so that your drawing from the port tank. If the port tank is filling, then it's likely that the valve from the stbd tank is passing

[senormechanico]

You need to sell the boat and get a multihull. Problem solved.

[SkiprJohn]

I'm not familiar with powerboats as much as sailboats so will only offer a suggestion. It appears that the equalization line is acting exactly opposite to what you want. Is there some sort of pumping or coupling device in that line that could be installed backward?
kind regards,

[Jim Cate]

Originally Posted by GordMay

FWIW: The Fuel Return Lines MUST ALWAYS return to the tank from which the fuel was drawn.

G'Day Gord,

Why is that? I often draw from my keel tank and return to a saddle tank to shift fuel. Never had a problem with this, wonder what I am missing here?

Cheers,

Jim

And apologies for thread drift

[captain58sailin]

If you don't draw and return to the same tank you run the risk of overflowing your tank. If you are paying attention you might be able to correct a slight list drawing from one tank and returning to the other, but it is a risky process that one person should be assigned to monitor and have no other duties. Your cross over valve will not equalize your tanks if the list is too great, all the fuel will migrate to the lower tank. I would look very carefully at all of the valves and make sure they are all closing and opening fully. If they are correct, I would look to what you may have aboard equipment wise that can be moved to correct you list. If all else fails you might have to just run with one tank less full than the other. Even if you have twin engines, there might also be a difference in the fuel consumption between the two, they should be close, but you never know.

[DeepFrz]

Most people leave the crossover valve closed until they can manually observe the fuel levels. This is to prevent just exactly what you are experiencing. Switching the fuel tank in use every few hours should keep your tanks relatively even.

If I leave the equalization line off and run the genset in about
4-6 hours the fuel return from the genset into the port tank will fill that tank; it will equal the boat out until overflowing that tank

Return line should always return fuel from the tank the engine is drawing from.

You actually should have a fuel feed manifold and a fuel return manifold.

[Jim Cate]

Originally Posted by DeepFrz

Return line should always return fuel from the tank the engine is drawing from.

Y

You guys keep saying this... tell me just why it is so, please!

As I said, I have drawn fuel from my keel tank and returned it to a saddle tank as a mans of fuel transfer... for years, and not had a problem. Why is this so wrong?

Jim

[IslandHopper]

Jim imagine all your tanks are full, if you have your return going to a tank that is already full and not in use, you run the risk of overflowing that tank....

The level of the tank in use will always be dropping faster than the return fuel line will be delivering fuel to it....

With wing tanks especially you will be burning from one side and moving the return fuel to the opposite, resulting in listing and possible overflowing....

[Hudson Force]

Originally Posted by Jim Cate

You guys keep saying this... tell me just why it is so, please!......................

Obviously, the wrong thing to do would be overflowing your fuel tanks. Certainly, a person can be careful, when returning fuel to a different tank, so that this doesn't happen. Always returning the fuel to the tank that it is drawn from is just a safeguard against doing something stupid and we are all at risk when it come to human error.

[Pelagic]

Welcome to CF
Very familiar with these types of problem.
As you already learned, leaving the equalization valve open can create large lists which you may not even be aware of if you have a strong cross-wind so:
Rule #1…
Never..ever run with equalization valve open and label, do not open underway!!

Try this Voyage trial:

• Keep equalization valve closed and set manifold so each engine draws and returns from its respective Pt/Stbd Tank (SOP)
• Bunker to your desired amount but with slightly less in Stbd side, so that you have no list. (Make a note of how less it takes)
• Do not run Generator underway for at least a few hours of steaming.
• Anchor in quiet place and see if you have developed a list?

If No: then there is no problem and just allow for Gen consumption and switch Gen supply to heavy side when at anchor.
Also your calculated difference in amount when you bunkered will indicate how much movable weight you need to shift to Stbd side if it still bugs you.

If Yes: A couple of obvious possibilities:

• Given the age of your boat you might have a slight leak in the equalization gate valve when closed, that will require cleaning and reseating or replacement
• Not equal loads between 2 engines, with one returning more fuel than other. (more difficult to remedy as it can be inherent in power train or difference in fuel pump performance)

With fuel manifolds, you really don’t move them that much unless you have 5 or 6 fuel and day tanks.
Just keep in mind to close them firmly and when you open…open all the way then back down a quarter turn so the gate valves do not seat and freeze open.

Hope this helps and let us know how it goes.

[Florida Mike]

I would start by putting in a independent tank selector valve for the generator and its return line. Also make sure there is a valve in the main manifold that will isolate both engines from each other as a minimum, as the manifold will act as a equalization line. You would be better off in my opinion to have a manifold for each engine of the pickup and return so that you can control where the fuel comes from and it returns to. I doubt that the water heater balances out the generator. You might try shifting your house batteries to the high side until the boat evens out. Just my two cents, Mike.

[Jim Cate]

Originally Posted by IslandHopper

Jim imagine all your tanks are full, if you have your return going to a tank that is already full and not in use, you run the risk of overflowing that tank....

The level of the tank in use will always be dropping faster than the return fuel line will be delivering fuel to it....

With wing tanks especially you will be burning from one side and moving the return fuel to the opposite, resulting in listing and possible overflowing....

Well, IH, that is certainly true. But as I said, I use it to transfer from a keel tank to a saddle tank. The reason that I do this is the saddle tank being low or empty. It isn't rocket science to pay attention and stop long before the receiving tank is full.

And my 120 L saddle tanks don't seem to cause listing... my 400 L water tanks only cause a couple of degrees, full to MT. On long passages I tend to try to use the leeward tank, but I reckon that this is pretty silly in the big picture!

So sure, MISuse of this transfer method could cause a problem... misuse of many things can cause problems! I was really reacting to the statement (originally by Gordy, who is seldom in error) that one MUST return fuel to the source tank.

Cheers,

Jim

[Pelagic]

Nothing wrong with what YOU are doing Jim, as it is a controlled transfer and standard practice.

However we are talking apples and oranges here with the OP’s problem of 3 engines and 4 tanks. ‘Twin fuel tanks port and starboard with sight glasses that can be turned off or on’

• It is assumed OP understands that you never fill up tanks completely, but allow for Ullage. (Expansion)
• Also a safety note, never to leave sight glasses open while underway

If OP runs his Gen continually away from marina then making sure the gen’s return fuel goes into same tank as supply automatically avoids pressing up tank to overflow via the vent.

For OP…..Fuel management is far more critical on twin engine power boats than sailboats, so you should have a decent fuel transfer pump as Jim describes.

1. Ideally you should identify which Port Tank and Stbd Tank is what you can call your “Clean Fuel Oil Tanks” (P-1/S-1).
2. Base decision on best trim of vessel when they are full and other same side tanks are empty
3. Before taking on new fuel, transfer remaining fuel from (P-2/S-2) tanks to Ullage level thru a good filtration
4. On larger yachts we would transfer to (P-1/S-1) and continually recirculate/polish fuel using a centrifuge, but filters work ok.
5. New Fuel is put into (P-2/S-2) tanks, so that any new bad fuel does not contaminate what you know is good in (P-1/S-1)