Fuel transfer between tanks

[paulga]

The fuel tanks one on each side of the boat are connected via the thick braided blue hose. The control valve is open, so the fuel should be drawn from both tanks in which the diesel should always have the same level. But the portside fuel gauge shows "17" while the starboard side is at the "21" mark. What could lead to the tilt?

 

[AnsleyS]

Paul,


Uneven draw from two tanks may be due to the amount of suction each tank line has when the engine is running and it also may be due to an uneven fuel return from the engine to the tanks. Once a vessel starts to list to one side, an open transfer line can make the listing worse by equalizing the fluid heights of the two tanks. The high tank looses fuel to the low tank which makes the high side lighter and that increases the listing and causes more fuel to flow to the down side and again and again.


I suggest that you close that valve, pump fuel into the high side until the boat is level or the gauges are equal and then take a run and see where the fuel comes from and where it goes back. You may have enough valves in your system that you can manage the fuel flow from both tanks to keep you level.

 

[Cigatoo]

Simple stuff first. Make sure both tank vents are un obstructed. Critters love to build their nests in the vent tubes. Tubes can be kinked also. Blowing a shop vac into the fill will give you an idea if the vents are clear. Have someone near the vent outlet.

 

[paulga]

Blow the shop vac air nozzle at the fuel fill?

I have not seen the fuel tank vents yet. Where are the vents usually located?

Simple stuff first. Make sure both tank vents are un obstructed. Critters love to build their nests in the vent tubes. Tubes can be kinked also. Blowing a shop vac into the fill will give you an idea if the vents are clear. Have someone near the vent outlet.

 

[Cigatoo]

Yes blow the vac into the fill. I don’t know where yours are. Usually not far from the tank on the topsides

 

[paulga]

Yes blow the vac into the fill. I don’t know where yours are. Usually not far from the tank on the topsides

There are two louvers on each side, do these work as both ER vents and tank vents? these louvers likely are located behind salon closets, so they are not accessible easily. There are no through hull fittings on the topside.

The fuel fill is under the carton box in the photo

 

[O C Diver]

If you close the valves and level the 2 tanks with the pump, does the boat have a list? This may be hard to measure and may need to be done on the transom to the waterline.

Many boats have a list based on galley, batteries, water tanks, holding tanks, or other items to one side as opposed to the other. As an example: my boat has the galley, one water tank, and the holding tank on the same side. I ballasted mine to eliminate most of it. Obviously whether the holding tank and one water tank are full or empty, makes trimming the boat an every few day adjustment.

If I had to guess, based on the valve to isolate the tanks and the transfer pump, I'm guessing fuel is used to trim the boat.

Ted

 

[PhilPB]

There are two louvers on each side, do these work as both ER vents and tank vents? these louvers likely are located behind salon closets, so they are not accessible easily. There are no through hull fittings on the topside.

The fuel fill is under the carton box in the photo


View attachment 144538

A tank vent is generally 5/8" line off of the top of the tank. Go into your engine room and look for a hose from the top of the tank that leads to a fitting on the hull.

 

[paulga]

A tank vent is generally 5/8" line off of the top of the tank. Go into your engine room and look for a hose from the top of the tank that leads to a fitting on the hull.

inside the ER the fuel tanks are completely behind the insulation panels. so I cannot see the top of the tanks

 

[Portage_Bay]

The term topsides refers to the hull from the waterline up to the deck level. Even if you can't see the tanks you will know where they are. Look on the hull near the tanks at a level higher than the tops of the tanks. You're probably looking for a fitting similar to these.

 

[Sailor of Fortune]

where are the return lines emptying to?

 

[paulga]

The term topsides refers to the hull from the waterline up to the deck level. Even if you can't see the tanks you will know where they are. Look on the hull near the tanks at a level higher than the tops of the tanks. You're probably looking for a fitting similar to these.

You are correct, so those 3 "bolts" are likely the vents. I never looked at them from underneath.

So each tank has 3 such vents? The chance that all 3 vents are clogged is very low, right?

 

[Delta Riverat]

Usually 1 vent per tank. But that's for all your tanks. Fuel, water and waste, 1 vent per tank.

In my case that's 9 vents.

 

[Comodave]

Usually 1 vent per tank. But that's for all your tanks. Fuel, water and waste, 1 vent per tank.

In my case that's 9 vents.

That is usually the case. You need to identify which vent goes to which tank. One is likely water, one for holding tank and one for fuel. Just hold your hand by the vents when filling the water and fuel and you should feel air coming out. As to the waste tank as said above you can use a shop vac blowing air in through the pump out fitting, gently so you don’t over pressurize the tank, and you should feel air coming out of the holding tank vent if it isn’t plugged. It may be plugged so that is why you don’t over pressurize it. It could be plugged with just waste or if there is a filter in the vent hose it could be plugged, not an uncommon event. But you do need to know which vent goes to which tank and make sure the vents are in working condition.

 

[AusCan]

As mentioned in post #2, sometimes opening an equalizing valve makes the list worse.
Take notice of where all your tanks are.

I keep my all my equalizing valves shut, and manage the boat level by alternating water tanks which are further off the centreline. They have the biggest affect on causing a list.
A boat that has high fuel usage may have to be managed by alternating fuel tanks when needed.

 

[paulga]

Most likely the vents location are close to the tank

Any remedy if a vent is somewhat clogged by dust or debris?

 

[paulga]

I just checked, the engine and Genny both get fuel from the starboard tank, Genny return to portside, engine fuel return to starboard side. So if I close the equal valve, I will be using the starboard side tank only.

If I have a diesel heater taking fuel from the starboard side tank, with the equal valve open, diesel is supposed to flow to the starboard side to score a balance. But as the starboard side gets lighter, boat lists to the portside, maybe before the fuel had time to flow to starboard.

As mentioned in post #2, sometimes opening an equalizing valve makes the list worse.
Take notice of where all your tanks are.

I keep my all my equalizing valves shut, and manage the boat level by alternating water tanks which are further off the centreline. They have the biggest affect on causing a list.
A boat that has high fuel usage may have to be managed by alternating fuel tanks when needed.

 

[paulga]

I found there is a valve at the forward top of each of the fuel tanks. The valve is open on the portside but closed on the starboard side. There is a copper fuel line in between the valves.

What are there valves for?

 

[Portage_Bay]

Looks like the valves are the upper sight gauge shut off valves.

 

[paulga]

Looks like the valves are the upper sight gauge shut off valves.

the sight gauges work on both sides. I just closed the equalization valve and activated the transfer pump to move some diesel to the starboard side. now both gauges read ~18.5

to clarify, there are two valves (looks the same) on each side. the gauge shut off valve is behind the valve shown in the photos

 

[Mako]

inside the ER the fuel tanks are completely behind the insulation panels. so I cannot see the top of the tanks

I've been looking at a few 1980's Taiwan trawlers lately and I've been seeing this more and more. Those panels are worthless for sound absorption and only work for (slightly) knocking down reflection.

Do you think they are really worth keeping, or have you considered ripping them out so the tanks are fully exposed visually?

 

[Portage_Bay]

Without being able to put eyes on the system and trace the lines I can't guess what those extra valves and tubing do,


The suggestion to strip out the tiles is in my opinion a sound one. It's always a good idea to be able to keep an eye on all things fuel. Especially on older boats. With all that out of the way you'll be able to trace everything and fully understand your system

the sight gauges work on both sides. I just closed the equalization valve and activated the transfer pump to move some diesel to the starboard side. now both gauges read ~18.5

to clarify, there are two valves (looks the same) on each side. the gauge shut off valve is behind the valve shown in the photos

 

[paulga]

The panels are mounted with lots of stuff.
Where do these stuff mount without the panels?

Without being able to put eyes on the system and trace the lines I can't guess what those extra valves and tubing do,


The suggestion to strip out the tiles is in my opinion a sound one. It's always a good idea to be able to keep an eye on all things fuel. Especially on older boats. With all that out of the way you'll be able to trace everything and fully understand your system

 

[Portage_Bay]

The suggestion is to remove the sound tiles, the stuff with holes in it. It is not structural. Your "stuff" appears to be mounted on plywood panels which are attached to framing. The ply panels and framing are what carry your system components.

Your systems appear to be well laid out and labeled. Maybe you can remove enough of the sound tiles to solve your mystery. Learning a boat's systems is a voyage of discovery and is best accomplished in person, hands on. You'll get there. You've already learned a lot since you've been posting here.

 

[mvweebles]

Paulga - you need a schematic of your fuel system to figure this out. It will take some time, but you will save yourself some headaches if you trace each line and do a sketch, even a simple hand drawn one. Previous owner of your boat had a good start by labeling the important valves, but you would be well-served to trace the supply and return lines with all interim valves and any pump. Given the age of your trawler (and the common construction conventions at the time), anything that goes into the top of the tank is either vent or return. Anything that comes off the bottow is supply.

Attached is an example of mine, though an early iteration (the scattered valves were replaced with a manifold). I've called-out manufacturer and model of each component which is not necessary for you - just "VALVE" or "TEE" is more than enough.

While I understand suggestion to remove sound tiles, as you note, it's a much more complicated project than just removing the tiles. They appear to be in good shape - I wouldn't touch them until needed.

Peter

 

[paulga]

Thanks for pointing out the frames. I thought the components are mounts on the panels.

it seems not possible to remove those dotted tiles without first removing the cluttered stuff, those zip tied cables/lines and the plywood panels. this type of project does not fit my time budget now.

The suggestion is to remove the sound tiles, the stuff with holes in it. It is not structural. Your "stuff" appears to be mounted on plywood panels which are attached to framing. The ply panels and framing are what carry your system components.

Your systems appear to be well laid out and labeled. Maybe you can remove enough of the sound tiles to solve your mystery. Learning a boat's systems is a voyage of discovery and is best accomplished in person, hands on. You'll get there. You've already learned a lot since you've been posting here.

 

[paulga]

Thanks for showing the example plot

I could see the engine/genny fuel return fittings on the tanks. I was not able to trace from the top valve much further. if it is also for fuel return, with the starboard side shut off, the previous owner may intentionally set the fuel return to the port side, probably to prevent too much fuel flow to the starboard side

Thanks for pointing out the frames. I thought the components are mounts on the panels.

it seems not possible to remove those dotted tiles without first removing the cluttered stuff, those zip tied cables/lines and the plywood panels. this type of project does not fit my time budget now.

 

[Mako]

Thanks for pointing out the frames. I thought the components are mounts on the panels.

it seems not possible to remove those dotted tiles without first removing the cluttered stuff, those zip tied cables/lines and the plywood panels. this type of project does not fit my time budget now.

Following to this conversation between you and @Portage, it appears that the plywood which your components are mounted to block 2/3 of the visible area, so removing the perforated tiles won't gain you much.

Visibility is very important for catching trouble early on. If your fuel tanks, which are hiding behind those panels, are steel, then you want to keep an eye on them especially for water tripping from the deck above.

Understood that you don't have a lot of free time now, but in the future if you wish to address this, then I'd suggest building some sort of framework skeleton (out of 2x2 wood, or steel tubing if you can weld) to replace the plywood. That way you can easily see behind the components for an occasional inspection. That would also be a good opportunity to clean and give your tanks a fresh coat of paint.

 

[paulga]

Thanks for the suggestion.
if I could take on this project, it may provide an opportunity to upgrade to GRP tanks, as the tanks would be within access, with those peripherals out of the way.

so just being curious, is steel tubing lighter than what 2x2 wood framework weighs?

Following to this conversation between you and @Portage, it appears that the plywood which your components are mounted to block 2/3 of the visible area, so removing the perforated tiles won't gain you much.

Visibility is very important for catching trouble early on. If your fuel tanks, which are hiding behind those panels, are steel, then you want to keep an eye on them especially for water tripping from the deck above.

Understood that you don't have a lot of free time now, but in the future if you wish to address this, then I'd suggest building some sort of framework skeleton (out of 2x2 wood, or steel tubing if you can weld) to replace the plywood. That way you can easily see behind the components for an occasional inspection. That would also be a good opportunity to clean and give your tanks a fresh coat of paint.

 

[MichaelD]

If I understand correctly, the two tanks are interconnected by the blue hose. Then the fuel level should equalize naturally. Have you considered the guage readings might be just a calibration issue? You said 19 and 21 are the readings? What % of full scale is that? Maybe it’s inconsequential.