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Old 11-29-2016, 01:07 PM   #1
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Fuel tank equalization

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
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Old 11-29-2016, 01:33 PM   #2
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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?
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Old 11-29-2016, 01:46 PM   #3
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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.
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Old 11-29-2016, 02:37 PM   #4
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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.
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Old 11-29-2016, 03:07 PM   #5
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Many thanks. I'll stick the tanks in the morning but it has to be unequal fuel loads. Bill
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Old 11-29-2016, 04:11 PM   #6
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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.
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Old 11-29-2016, 04:20 PM   #7
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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.
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Old 11-29-2016, 05:03 PM   #8
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ABYC H33 Diesel fuel systems ... (paraphrased) All fuel must return to the tank from which it is drawn.
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Old 11-29-2016, 07:16 PM   #9
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Quote:
Originally Posted by Bill21 View Post
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
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.
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Old 11-29-2016, 07:31 PM   #10
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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.
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Old 11-29-2016, 07:38 PM   #11
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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:

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Old 11-29-2016, 07:58 PM   #12
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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?
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Old 11-29-2016, 08:32 PM   #13
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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.
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Old 11-30-2016, 11:16 PM   #14
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Quote:
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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.
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.
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Old 12-01-2016, 09:41 AM   #15
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.......but it has to be unequal fuel loads. Bill
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.
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Old 12-01-2016, 12:10 PM   #16
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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.
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Old 12-01-2016, 12:13 PM   #17
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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...
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Old 12-01-2016, 12:15 PM   #18
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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..
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Old 12-01-2016, 12:40 PM   #19
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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.
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Old 12-01-2016, 12:57 PM   #20
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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.
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.
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