Fuel tank equalization

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Bill21

Newbie
Joined
Nov 29, 2016
Messages
3
Location
United States
Vessel Name
LONGFELLOW
Vessel Make
Mainship I 34
Recently bought a 1982 Mainship 34 after years of sailing. Confronted with a distinct list to port and assuming it is caused by an unequal fuel load. Lines from both tanks are open. Starboard tank reads half full, port tank reads empty but suspect sender is inoperative as that is the low side of the boat. Bilge is empty and water tank amidships. Any suggestions will be greatly appreciated. Bill
 
Do you have a cross-over line and valve between your fuel tanks? If you do, open the valve so the two tanks can equalize. Do you have sight tubes on the tanks? If not, can you "stick" the fuel levels in each tank from the deck fill?
 
No cross over line that I can see. Both lines meet at the first fuel filter, a spin on Racor then one line to the motor. Both lines have shut off valves just before the filter. Return line to port tank only. I'll try and "stick" the tank when I can find a stick. Probably in a nearby yard in the morning. Filters replaced. I just ran the motor on the port talk only but only for a couple gallons, maybe 25 lbs or so. Thanks for your help.
 
If you return to only the Port tank I would bet that your Port tank is much more full than the starboard.

If it was me I would use a stick, fill up both tanks, and then start with running from the Port tank only. When you start to list to starboard then run on both tanks until the list is gone or you can measure the tanks. Since you only return to the Port tank, I would not recommend running on the Starboard tank only.

Fix the sender and consider adding sight tubes at some point.
 
Many thanks. I'll stick the tanks in the morning but it has to be unequal fuel loads. Bill
 
The OP's boat is a 1982. I can't believe that for 34 years all previous owners have fought with a one engine, two tank, one return line system.
First, the builder would never (OK, some may in fact be brain dead, but I would give them the benefit of the doubt first) leave a single return system without allowing equalization, likely by way of a crossover line that is now behind stuff that has made it difficult for the OP to find.

Once you find the crossover and open it, transfer some other weight to encourage the fuel to equalize, once level, transfer stuff to keep it level, then leave the crossover open.

If there is in fact no crossover, put one in. Put a valve in an accessible position, leave it open.
 
Is there a genset drawing on the less full tank? Anything is possible, when I bought my boat the genset was drawing from one tank and returning to the other.
As this is a recent purchase tread carefully. There could be a reason one tank is filled to a lower level.
 
ABYC H33 Diesel fuel systems ... (paraphrased) All fuel must return to the tank from which it is drawn.
 
Bill21 said:
Recently bought a 1982 Mainship 34 after years of sailing. Confronted with a distinct list to port and assuming it is caused by an unequal fuel load. Lines from both tanks are open. Starboard tank reads half full, port tank reads empty but suspect sender is inoperative as that is the low side of the boat. Bilge is empty and water tank amidships. Any suggestions will be greatly appreciated. Bill
Click to expand...

I have a 1986 Mainship 36DC. I list to starboard - very noticable. Might have something to with the 2 house batteries on the outer edge of the starboard hull in engine room. Also, probably just from owner storage - the port side is pretty ,uch taken up wuth the fridge and small narrow cabinets. The starboard side has more room for stuff and stuff ain't light.
Fuel gage readings are notoriously wrong. I made a sounding stick. On my 36DC, the deck fuel fill is directly above the fuel tanks. I took a 3/8" oak dowel 48" long and epoxied and pinned it into a skinny PVC pipe. My tank is 120 gals and is 24". After the simple math 120 Divided by 24, you get 5 gals per inch. Not to get crowded, mark the stick at 2" Intervals for 10 gals. per mark. You can very accurately measure and judge the amount of fuel you have. When on a very long trip, I will fill up to the 110 gal mark. That will give me 2" clearance from the top of the tank. Dont want to have gasoline sitting in the fill hose. Normally never fill past the 100 mark.

Use oak dowels. Birch and pine wont suck up the gas and so its hard to read the stick. I have 2 sticks. I marked my sticks with indelible markers. they will smear if you wipe them. So use one stick in each tank. They will dry completely in about 5 minutes. If you smear them more than a 1/2 dozen times or so, they become difficult to read.
 
I would take inventory of what weight you have where. And see if one side outweighs the other generally.

I have a slight list to port, but that is the side that 12 golf cart batteries are on, one start battery, plus both FB helm chairs and FB seating. the galley is to port as well. The master bed is mostly to port.

Major items to starboard are genset, full size fridge freezer, a start battery and two genny starts, but that is pretty much it. The water and holding tank are centered.

I did talk to the yard about ballast. But I don't think adding weight to the boat to remove a list is worth it. So I just keep the starboard tank fuller, though the genny runs from that so can be a bit of a battle.
 
I inspect the boat's trim and change fuel draw from one side tank to another, or use a small pump to move the fuel. A result of filling only one of the starboard fuel tanks:

 
I never try to equalize or draw fuel from both thanks. If I'm in trim I usually draw from the tank I think has the oldest fuel and switch when I notice a slight list. Then switch whenever there is a need. Or if I feel like it dip the tanks and draw from the one w the most fuel. Why do anything else?
 
Personnally I draw fuel from both tank and they tend to equaoize by themselves. First half port is going down faster then starboard is going down faster. When both are half port is going down faster till the mlast quart then starboard again and when reaching the last quart the draw is pretty equal on both. Maybe due to the return line or the equalizing line I dont have a clue but it has never been a real issue. When port is half and starboard have more the list is there but very slight and is not really annoying.
 
Tony B said:
I made a sounding stick. On my 36DC, the deck fuel fill is directly above the fuel tanks. I took a 3/8" oak dowel 48" long and epoxied and pinned it into a skinny PVC pipe.

Not quite sure why you did that, was it to lengthen the stick? I just use a longer dowel that reaches and painted the top 3-4 inches white so I know which end is which. But otherwise, good way to do it.

My tank is 120 gals and is 24". After the simple math 120 Divided by 24, you get 5 gals per inch. Not to get crowded, mark the stick at 2" Intervals for 10 gals. per mark. You can very accurately measure and judge the amount of fuel you have.....I marked my sticks with indelible markers. they will smear if you wipe them. So use one stick in each tank. They will dry completely in about 5 minutes. If you smear them more than a 1/2 dozen times or so, they become difficult to read.
Click to expand...

I don't know what timber my dowel was made from, but I just etched a groove into the dowel with a sharp knife as a ring round it at the marked levels, then they are permanent marks which stand all sorts of abuse.

As to the listing. To the original poster, Bill21. My system is simplicity itself, but then I just have Lehman engine, but the fuel return just goes back to the primary filter, so uneven feed-back to tanks a non-issue. The draw off from the tanks is from the bottom, and both lines join before the primary filter, so equalisation also never an issue. I suggest to the OP (Bill21) that you organise something like that.

But if, as you say...

No cross over line that I can see. Both lines meet at the first fuel filter, a spin on Racor then one line to the motor. Both lines have shut off valves just before the filter. Return line to port tank only.

Then, if that's the case, leaving both taps there before the filter open might allow them to equalise at that point as long as that filter is below the fuel levels, saving rigging up yet another connection. Have you tried that? After all, it might be why the PO didn't have a problem..? Then the return fuel line going to just one tank would not matter either, as they would just equalise as you go along.
 
Last edited:
Bill21 said:
.......but it has to be unequal fuel loads. Bill
Click to expand...

You may be correct. But this is a very expensive attitude when trying to solve boat problems. Keep an open mind so you won't have to open your wallet as much.
 
This is a normal situation on that vintage Mainship, There is no crossover to balance the system, all fuel from engine or gen returns to the port tank. Without doing a replumb job the only control you have is the valves that control which tank the fuel is drawn from. On mine, it will develop a starboard list over time also and I shut the port tank off and as you use fuel it will gradually return to a more level attitude, just don't go too far as you could overfill the port tank (never had it happen yet) but see nothing to stop that possibility.
 
if that's the case, leaving both taps there before the filter open might allow them to equalise at that point as long as that filter is below the fuel levels, saving rigging up yet another connection. Have you tried that? After all, it might be why the PO didn't have a problem..? Then the return fuel line going to just one tank would not matter either, as they would just equalise as you go along.

Don't think this will work either as the fuel lines exit the top of the tanks - at least I've never seen it do it on mine...
 
A simple Walbro pump and a 3 way valve will allow you to balance the tanks. Very inexpensive at less than $200 and allows fuel filtering/cleaning while at the dock depending on where you place the valves..
 
34' Marine Trader was the same way.

1982 boat, no crossover was ever installed.
Drove me nuts for a bit, as I originally thought that I had a clogged pickup, and was only running on the port tank.
After pulling the pickup on the starboard tank, which was clean as a whistle, started to take a closer look at things and discovered no crossover line.
My solution was the easy way out.
1) Run for approx. 7hrs from starboard tank.
2) Run for approx. 5hrs from port tank.
3) Go to 1.

I actually never really timed it...I'd just notice one day a very slight list to starboard, so I'd hit the valves before our next trip.
 
rhakct said:
This is a normal situation on that vintage Mainship, There is no crossover to balance the system, all fuel from engine or gen returns to the port tank. Without doing a replumb job the only control you have is the valves that control which tank the fuel is drawn from. On mine, it will develop a starboard list over time also and I shut the port tank off and as you use fuel it will gradually return to a more level attitude, just don't go too far as you could overfill the port tank (never had it happen yet) but see nothing to stop that possibility.
Click to expand...

I am a bit confused. The OP said that he has a list to port. If both tanks are open and the fuel return is to the port tank, then running with both tanks open should develop a list to port over time wouldn't it? This assumes that the fuel draw from each tank is equal.
 
Common problem with clogged lines. Have them "blown" out and back flushed. Also, recommend youchave the tanks cleaned.
 
Not my intend to hijack the thread (sorry PO) but all these posts raised a question in my mind (or what is left of my mind).
My diesel return line is returning not to one of my fuel tank but to the fuel line just before the primary filter. Is this something common, normal or not desirable?

l.T.
 
Lou_tribal said:
Not my intend to hijack the thread (sorry PO) but all these posts raised a question in my mind (or what is left of my mind).
My diesel return line is returning not to one of my fuel tank but to the fuel line just before the primary filter. Is this something common, normal or not desirable?

l.T.
Click to expand...


Some engines do that. Some engines pump only a bit more than they actually use thus return only a small portion of the fuel back to the tank. Sometimes those engines plumb the return line directly to the fuel filter.

Some engines pump a lot of fuel and use only a smaller portion of the fuel pumped. These engines almost always return to the tank. On these engines the return fuel will be very , very warm and use the tanks as a heat sink.

There is a catch to the first group and that can be from any air picked up from a leaky injector or from a leaky fuel pickup line. That air will accumulate at the filter and shutdown the engine by air binding the injection pump.. It will become impossible or very difficult to purge the air. The return to filter or injection pump type engine will not run untill the source of the leak is repaired.

The return to tank engines will purge the air to the tank where it can escape. Some engines, many are not, are capable of purging small amounts of air from the injection system so if the leakage is then dumped back to the tank the engine can run, maybe roughly , but it will run.
 
C lectric said:
Some engines do that. Some engines pump only a bit more than they actually use thus return only a small portion of the fuel back to the tank. Sometimes those engines plumb the return line directly to the fuel filter.

Some engines pump a lot of fuel and use only a smaller portion of the fuel pumped. These engines almost always return to the tank. On these engines the return fuel will be very , very warm and use the tanks as a heat sink.

There is a catch to the first group and that can be from any air picked up from a leaky injector or from a leaky fuel pickup line. That air will accumulate at the filter and shutdown the engine by air binding the injection pump.. It will become impossible or very difficult to purge the air. The return to filter or injection pump type engine will not run untill the source of the leak is repaired.

The return to tank engines will purge the air to the tank where it can escape. Some engines, many are not, are capable of purging small amounts of air from the injection system so if the leakage is then dumped back to the tank the engine can run, maybe roughly , but it will run.
Click to expand...


Thank you verynmuch for this information!
For what I know, my engine is consuming very small diesel and is very rudimentary and as it is running like this for quite some time I would tend to think it is fine but if anybody think it is not I am open to comments. On the temperature side it is fine, I checked the return line with a heat gun and the temp is on the normal side.

One other thing that will make other people jump 2 feet above their chair is that I have a single fuel filter! While this makes me a bit nervous and I tend to want to add more, my engine can run on anything can could be ran or almost. I found people thatbwere ablenmto run it using old engine oil, cooking oil, or even more exotic hydraulic oil or transmission oil! So as it is running with one filterbfor 20 years (ormore) and as boat diesel is the same as car diesel up here, I guess that is fine.

L.T.
 
And I have I have none this what makes me a bit nervous :)
Is it possible to add one? What kind? Any impact on the fuel pump? I really do not know!
 
Easy add in line. Can't believe there is not a pair of canister filters on engine. Add another Racor with bypass valve in case 1st one gets clogged. Also allows filter replacement and sump drain while underway. You can stagger fuel micron filter size. Maybe 20 on the 1st 20 on second..
 
Mr MV, my engine is kindof very rough one and old one that came from military trucks to fishing boat to my boat from the hands of a pretty good diesel mechanic (by pretty good I mean a guy who was a mechanic, who bought a hull, built a boat on top of it, rebuilt an engine before put it in this boat, so better than I will ever be).
From what I know from old papy diesel for cars and other things filtering was not very high tech .
This said I fully agree I should add a secondary filter and more a last chance filter before the pump. The only reason it is not done yet is because I do not know if there is any impact on the fuel pump. I do not want to **** up a working system.
 
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