Boat lists due to wanting fuel only from 1 side

[Ski in NC]

If you have a twin engine boat and two side tanks, leave the cross tie closed and let each engine eat out of it's respective tank. All boats should have valves available to set this flow path up. Gennie burn is usually negligible so can be fed from one or the other.

Leaving tanks connected often does cause problems with tank trim.

 

[Riverguy]

A balance tube from one tank to the other. I'm surprised it was not originally set up that way

In many boats, it is not possible to have a passive balance hose/tube between tanks. For example, our Mainship 390 has one...but our Bayliner 4788 does not. If you were to crawl down there in both boats, you'd see it's easy on the Mainship but not possible on the 4788 due to the location of the tanks. The Jefferson configuration (IIRC) is very similar to the 4788.



There is also a 'debate' around fuel contamination. Connecting the tanks together creates 'one common tank'. If fuel in one tank is contaminated, they are both contaminated. Two entirely separate fuel systems, one for each engine, provides some redundancy.



Our 4788 has a transfer pump that moves fuel from port-starboard or vice-versa.

 

[kapnd]

Passive balance, or crossover tubes seldom work well for me.
There’s too many variables in loading and sea conditions for it to work as intended, and with the crossover valve open, I always wind up with too much fuel on one side, so I keep it closed, and alternate tanks.
The post about clearing vents is spot on, should be an annual maintenance item on everyone’s list. Clogged vents can raise hell in many ways, and it’s a problem that’s easily avoided.

 

[AusCan]

Leaving crossover lines open will make a a boat list more rather than less. Always keep the tanks isolated. Same with water tanks.

Think about it. A boat is listing slightly due to many possible reasons. With the crossover line open, the contents of the tank on the high side will want to flow to the low side making the boat list more and more and more.

If you want to balance the weight, do it by shifting the load or using water or fuel from the low side, but keep your tanks isolated from each other.

 

[BruceK]

Not sure about uneven weight causing fuel/water to crossover, though it certainly makes sense.
I had a visible list(later largely corrected by removing lead ingots from the ER low side)but when refueling always took about the same amount of fuel either side.

 

[catalinajack]

The Admiral and I have an 2002 Jefferson MY with exactly this problem. It's clearly nothing to do with fuel supply, crossover lines etc. because, as you said, with the fuel tanks at the same level and the engines not running the fuel will transfer itself from Port tank to Stbd tank and the boat will list. What's happening is that the boat is too heavy to Stbd and the fuel will move to the Stbd side because of this. With the boat sitting at it's natural list to Stbd the fuel will actually be balanced in both tanks relative to the horizon but the Stbd tank has much more fuel in it than the Port tank. Underway I keep the port tank supply line cracked open but not fully open and manage to keep close to level but I have to adjust it several times or transfer fuel during the day which is a real PIA. If their is any movable ballast in this boat I've not found it.

Movable ballast - can't find it? Buy some. I use recycled shotgun pellets in 25# bags. Got mine from Shyda's Outdoor Center in Lebanon, PA. Two bags with shipping costs $97. Our boat has a chest freezer and a 12kw generator on the same side. I have 600# stuffed away in unused spaces. To balance the boat I fill the water and fuel tanks and shift weight referencing a carpenter's level. Without the lead shot the boat will list unacceptably. Once I got her balanced with a full load-out, I only had to tweak it several times. Come to think of it, I haven't touched the shot bags in the last 3,000 miles of doing the Great Loop.

My fuel and water crossovers do not have shut-offs so lead weight is my only option. But I do have the option of running on one tank.

 

[Great Laker]

The Admiral and I have an 2002 Jefferson MY with exactly this problem. It's clearly nothing to do with fuel supply, crossover lines etc. because, as you said, with the fuel tanks at the same level and the engines not running the fuel will transfer itself from Port tank to Stbd tank and the boat will list. What's happening is that the boat is too heavy to Stbd and the fuel will move to the Stbd side because of this. With the boat sitting at it's natural list to Stbd the fuel will actually be balanced in both tanks relative to the horizon but the Stbd tank has much more fuel in it than the Port tank. Underway I keep the port tank supply line cracked open but not fully open and manage to keep close to level but I have to adjust it several times or transfer fuel during the day which is a real PIA. If their is any movable ballast in this boat I've not found it.

You have nailed it exactly. The problem is an imbalance and the answer is leveling by adding ballast. I used plastic bags of crushed stone tucked into a narrow unusable space behind one of the galley cabinets. The bags are flexible enough to adapt themselves into nooks and crannies and never harden, make noise or rust. I think it only took 3 - 20 lb bags to correct a two inch list.

 

[kapnd]

Wow, that sounds like a pretty tender hull!
I’ve got over a ton of lead in my hull, mostly down the center, with about 300# to starboard to correct a couple inches of list.
All that ballast has surprisingly little effect, I may take the bulk of it back out if I feel real energetic some day.

 

[Great Laker]

Wow, that sounds like a pretty tender hull!
I’ve got over a ton of lead in my hull, mostly down the center, with about 300# to starboard to correct a couple inches of list.
All that ballast has surprisingly little effect, I may take the bulk of it back out if I feel real energetic some day.

The further from the center line of the hull, the better the leverage of the ballast. My bags are 6ft from the center line and there is no other ballast in the hull.

 

[bgillroy]

You will needto be able to inspect, clear and repair of needed all venting Lines on the boat that is mandatory IMO. Easily said had to do, but necessary.

 

[DHeckrotte]

I’ve been reading posts on this topic for quite a while now. I affected fore and aft trim about 2”, and lateral trim by about 1”, by moving my two spare anchors and chain from the lazarette, port side against the transom, to on deck as far forward as they’d fit. Lateral trim is harder to maintain. The prevailing wind at our slip is from port. With open crossovers at the symmetrical fuel and water tanks, she lists to starboard. Annoying and unaesthetic!

There’s no way I care to grovel regularly in the ER, fiddling with valves, unless we’re off and running somewhere. Thinking more and more about adding transfer pumps to both fuel and water tanks. Seems pretty easy to do, and I can handle twiddling switches while sitting at the helm and watching fuel gauges and my little level.