Listing problem

Boat listing problem
I’m trying to figure out how to get rid of an ever changing list to starboard. 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 2-4 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 about 4-6 hours the fuel return from the genset into the port tank will fill that tank until overflowing. I am trying to figure out this problem without adding any weight to the boat does anyone have any suggestions.
Thanks.

It's possible your initial 2 to 3 degree list has nothing to do with your tanks at all. It may simply be because your boat is loaded that way. Just about anything from tool boxes to full refrigerators can cause a boat to list.

A not uncommon solution is to add some ballast down in the hull on the high side to eliminate the list. And since even an almost imperceptible list can cause fuel to move from one side of a boat to the other via a cross-connect line it's probably best to leave the valve on the cross-connect line closed unless you actually want to equalize the fuel levels in the tanks.

It sounds as if your gen set is being supplied from the starboard tank and returns to the port tank; causing your overflow problem. It seems to me that a simple solution would be just to change the gen set return line to the starboard side. Leave your equalizing line closed and running the gen set from the starboard tank would mean this tank would normally be less full than the other, balancing out your listing problem.

And Ksoul thinks he had a problem:



In the above situation, it was because fuel was added to the starboard tanks only.

I agree with Marin, you might want to try, with the fuel tanks at the same level and the boat listing, have a person or persons of known weight stand on the opposite side till the boat is level then add that much weight to that side or shift tool boxes, bar supplies, etc. to see if that will work.
Steve W

My last boat, A Nova Sundeck very similar to yours most like also had the same Starboard list but was solved? by the manufacture? but dumping a bunch of cement on the other side of the port side stringer.

Dave N

And i also forgot in addition to the cement, a bunch of lead bars in the lower galley seating area.

Dave N

Most if not all boats list to some degree. the Eagle list changes daily/weekly depending on how full the water tanks are, holding tank, and fuel tanks. It will start out the week listing to starboard and by the end of the week be listing to port. The Webasto draws in and returns from the port tanks so each week I have to transfer fuel from the fuel to the port tank. I balance the Eagle by the why the doors hang. The concern is when the boat is listing more than normal/expected.

I agree it sounds like the gen set is drawing from one tank but returning to the other. Should normally draw and return to the same tank.

On Gray Hawk I find that we typically get a small list to stb when the fuel tanks are close to full and as the OP suggested that list gets worse if the crossovers are open. We deal with that by controlling which water tank we are drawing from. If we are listing to stb I shut off the port water tank and draw exclusively from the stb tank until we are level again. Of course at that point I need to remember to go open the port water withdrawal or we will end up listing to port.

In our case it seems that we have less of a problem if the fuel tanks are 1/2 full or less (which is a situation I try to avoid but it happens). I'm no nautical engineer but I suspect it has to do with the location of the weight relative to the CG of the boat. Initially I tried to control the situation with the fuel valves because we have a very extensive manifold system that allows me to draw from either tank to either engine and to return from either engine to either tank. That was not very successful because it takes so long to burn any significant weight of fuel. Using the water tanks generally takes care of the problem within 24 hours.

I'm sorry I may not have been clear on my original post.The genset draws from the same fuel manifold that the main engines draw from and the genset fuel return is to the port tank. If I open the port and starboard fuel tank valves at the fuel manifold that means I am drawing fuel from both tanks. Some times the list i have to deal with with is as bad as the picture from Markpierce of the Carquinez Coot. Thanks everyone for such a speedy responce

Angelina lists to starboard every time she is run. The engine pulls from both tanks but returns only to the starboard tank. When we come back the next day, gravity has worked it's magic and she is right again.

That line between the two tanks should always be closed.
It could sink you.
Liquids always travel down hill.
If you are motoring along and one tank gets lower than the other the line between the two tanks could cause the full tank to become more so producing more an more of a list till she rolls.
I seen this happen in the harbor. The list got so pronounced from the fuel transferring form one tank to the other A through hull from a bilge pump went under water and filled the boat. She rolled over and sank to her lines.
Something to consider.

sd

On our boat there was only one return (to the port tank) no matter which tank (stbd or port) was being drawn off of. I added a return to the stbd tank and a manifold and valves to give choices. I keep the equalizer line closed (it doesn't do much anyway). I also added some lead ballast to the "high" side (using the known weight guest(s) standing on the high side method). Now I can pretty much keep the boat evened out side to side.

My best friend has a 1986 42 Jefferson Sundeck which also has a persistent list to starboard. Many of his major interior weights favor the stbd side; refrigerator and galley, settee, helm, sundeck wet bar. I got a call from him a few months ago while I was on the water. He got a call from the marina saying his boat appeared to be listing. He asked me to check it out since he was 3-4 hrs away. Turns out his crossfeed line was open and the fuel followed gravity to the stbd tank. Closed the valve and all was well.

If it was me, I'd keep that crossfeed valve closed unless balancing is actually required, monitor it while crossfeeding, then close it when done.

If you'd like to talk with him, send me a PM with your contact info and I'll ask Gene to call you. Maybe the two of you can compare notes and come up with a solution or technique that works. If adding ballast, be sure it it secured so it stays put in all boating positions, including inverted. The last thing you want is that weight coming loose at the worst possible time.

We're fortunate that all tankage (fuel, water, and holding) are centerline and integral to the frp hull. Our weight distribution concern is fore and aft. When the main fuel tank (400 gallons) and secondary tank (220 gal) are low on fuel, and we top off the fwd fresh water tank (525 gals) and have a full 60 gal holding tank, the stern rises up an inch or two. POs loaded what I'd estimate as 500 lbs of lead weights in the boat. I have moved about 250 pounds to the aft cabin to balance.