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Drawing from 2 Tanks - At the same time?
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| mattgeiger |
Posted on 10/14/09 - 2:00 PM
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Lying in bed last night no sleeping - my mind was wondering around my Montauk as usual.
I have twin tanks and a thirsty old Johnson 90.
Would it be feasible to connect both tanks to a "T" then run the main line to the motor? (soon to be going through a Racor FF/WS).
That way I don't need to worry about switching tanks. I would not need to worry about the starboard tank getting stale since I usually run off (lighten) the port tank to balance the boat.
Maybe I need need to wash down some Tylenol PM with a shot of Rum and just go to sleep...
Cape Dory 28
Hobie 20 Miracle
A Class Catamaran |
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| nvaccaro |
Posted on 10/14/09 - 2:05 PM
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I had the same thought when I bought my Montauk. The boys at West Marine told me it won't work. Honestly, I don't understand why it wouldn't, but I just went with the one tank under the seat. Good luck with that.
If you can't sleep, avoid the Tylenol PM and try a scotch and water. Always works for me 
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| Binkie |
Posted on 10/14/09 - 6:54 PM
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I`ve run a couple of boats with 2 permanent tanks, with a T fitting. The water separator was on the mainline going from the T to the engine. Only thing is the T was fitted to a handle that would switch from one tank to another, never both at the same time. Guess it would work, if both tanks were identical and always had the same amount of fuel in them. If not, one tank might run out of fuel, and start sucking air. I don`t think that would be a good thing.
Rich |
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| brorobin |
Posted on 10/14/09 - 7:40 PM
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Wondering how the -fuel bulb prime thing- might play into this equation. Maybe not at all. It seems that both tanks would have to have the same vacuum pressure to the T in the line.
Just wondering????, maybe I don't understand what I know (or don't know) 
Robin Chaplin
1972 13 Sport - 1994 25hp Mercury
It was my Dad's, now it's Mine, one day I'll pass it down, 'til then it's Happy Whalering. |
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| Guts |
Posted on 10/14/09 - 8:09 PM
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I see no reason you could not run two into one line , the problem would be if one tank went dry before the other one. but if you are that close on fuel? you would need to shout off the dry tank. Just thinking out loud here.
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| mattgeiger |
Posted on 10/15/09 - 4:48 AM
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Thanks guys. I think I'll add it to my project list.
Cape Dory 28
Hobie 20 Miracle
A Class Catamaran |
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| number9 |
Posted on 10/15/09 - 4:59 AM
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Shouldn't be a problem, you just want to set up your valveing to be able to draw individually from left or right and both. As Guts said drawing off of both with one tank empty is not going to work. The tanks in the trawler I had was set up that way. Many boats are set up that way to maintain trim and list.
Bill...On the Ogeechee
1984 Outrage 18...Yamaha T50...that's right, 50hp |
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| Finnegan |
Posted on 10/15/09 - 8:30 AM
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Without a 3-way selector valve, it won't be a 100% reliable system using only a Tee, as mentioned in above posts should one tank empty first. But then again, a Montauk using a selector valve, with no real good place to mount it, etc, is almost just as much trouble as switching tanks the old way. I'd leave things as is.
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| HarleyFXDL |
Posted on 10/15/09 - 12:19 PM
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Only thing I can think of would be the pressure in each tank due to the weight of the fuel. Seven gallons of fuel would have a different pressure than 3 gallons. Just a guess.
Kevin
1988 11' Super Sport, 1987 Johnson 15hp.
If you think education is expensive, try ignorance
"Vegetarian - old Indian word for bad fisherman." |
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| JohnnyCW |
Posted on 10/15/09 - 1:01 PM
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The tank pick-ups rise straight up through the top of the tank. If a tank has a higher fuel level, less lift will be required required to draw fuel from that tank. A tank with a lower fuel level will require more lift. If the tanks are physically the same and the fuel lines the same length and route, the draw will be about even from both tanks. The vessel not sitting level or some other such consideration may alter the fuel draw though.
I'd plumb both tanks to a T-fitting the plumb the T-fitting toward the filter/separator/motor. I'd also plumb in an in-line shut-off valve between each tank and the T-fitting. If things start to get too uneven, its a simple matter to shut off the tank with the higher level.
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| Binkie |
Posted on 10/15/09 - 1:11 PM
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You might be able to do this, you should try it. the question is WHY do you want to do this? what is the advantage?
Rich |
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| thetis |
Posted on 10/15/09 - 1:21 PM
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I am showing my age, but I seem to remember in the early sixties there was an accessory with OMC Cruise a day tanks that would allow you to run more than one tank similtaniously. Fuel would be pulled completely from one tank, then the next and so forth.
Does any one else remember this?
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| mattgeiger |
Posted on 10/15/09 - 3:25 PM
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Binkie wrote:
You might be able to do this, you should try it. the question is WHY do you want to do this? what is the advantage?
Many days I'll burn through a tank of gas then have to stop and pull the tanks to switch the fuel line. It would be nice to be able to run a full day with gear and family and not have to shuffle everything around to do so.
Not a big deal. Just thinking out loud about one more thing to maybe tinker with. I have other legit projects to tackle like the Racor filter and an auto bilge pump.
Cape Dory 28
Hobie 20 Miracle
A Class Catamaran |
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| JohnnyCW |
Posted on 10/15/09 - 3:32 PM
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I was curious about the idea so I tried an experiment with some fish tank tubing, a plastic T, and two glasses of water. I cut two 12" lengths of the tubing and attached them to the T then ran a couple of more feet of tubing from the T to an empty plastic jug. I put the end of each 12" piece of tubing into separate glasses. One filled half way with water, the other glass filled all the way to the top with water. I then started a siphon running the water into the plastic jug. Sure enough, only the level in the filled glass began to drop until the level of water was even in both glasses then they both seemed to empty at the same exact rate.
Worked well in a controlled environment.
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| number9 |
Posted on 10/15/09 - 3:33 PM
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Moeller says their 3-way valve allows drawing from one tank at a time only. Are all 3-ways designed that way? After reading that seem to remember my trawler had s/o valve for each tank prior to a t-fitting that then went to the Racor.
Each tank could be equipped with with a s/o valve plumbed to a tee.
The valves aren't cheap but it would be better to have them rather than just plumbing into a tee.
Bill...On the Ogeechee
1984 Outrage 18...Yamaha T50...that's right, 50hp |
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| scrimshaw |
Posted on 10/15/09 - 4:25 PM
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My Outrage has 2 19 gallon saddle tanks they are each connected to a selector on/off valve allowing to choose a tank beyond that the bulb and filter. I have run with each tank open just to see, the port always runs faster and eventually sucks air. Don't know why but it doesn't work.
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| JohnnyCW |
Posted on 10/15/09 - 4:31 PM
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scrimshaw wrote: I have run with each tank open just to see, the port always runs faster and eventually sucks air. Don't know why but it doesn't work.
The lines between the T and the tank need to be the exact same. Length, number of bends, elevation over and through obstacles and other variable will alter the flow between tanks. If the tanks are side by side, makes it easier.
Regardless, I still think it prudent to have a separate valve between each tank and the T. Even if it doesn't work well, its got to be a little more convenient to switch valves rather than unplugging the fuel line to switch tanks.
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| Guts |
Posted on 10/15/09 - 4:40 PM
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This is the way I would go...
Product Description
Moeller 1/4" FNPT Three - way Valve delivers US Coast Guard - approved anti - siphon protection of all gas - powered boats! SAVE BIG! Meets ABYC H-24 requirements, making this the safe choice for connecting 2 permanent tanks to 1 motor. All-brass construction, convenient hose barb design.
Edited by Guts on 11/06/09 - 10:17 AM |
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| number9 |
Posted on 10/15/09 - 5:28 PM
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Guts,
Problem with the valve you had links to,
"Product Description
Model: 033312-10
3-Way Valve, 3/8 FNPT
Constructed of brass, this valve meets ABYC H-24 requirements and provide anti-siphon protection. Connects 2 permanent tanks to a single motor. Provides withdrawal from one tank at a time only."
Bill...On the Ogeechee
1984 Outrage 18...Yamaha T50...that's right, 50hp |
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| Guts |
Posted on 10/15/09 - 5:35 PM
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number9 I am aware of this. I think Matt could go this way to prevent pulling out the tanks like stated in post # 13
This is the way it is done on most boats / gas or diesel. There are electric valves also.
QUOTE from post # 13 [(Many days I'll burn through a tank of gas then have to stop and pull the tanks to switch the fuel line. It would be nice to be able to run a full day with gear and family and not have to shuffle everything around to do so.)]
Edited by Guts on 10/15/09 - 5:39 PM |
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