Diesel Tank Question -> Return to AirVent?

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Bob Pullen HC-33 1981

Bob Pullen HC-33 1981

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Aug 20, 2006
220
Hunter 33_77-83 Yucatan, Mexico
Attached picture of fwd end of our Tempo 11.5 gal diesel tank, installed by Prev/Owner. Apparently he merely punched a hole for the "return" hose, since the other 3 connections were used up. The folks installing my new throttle cable, thought they could pull out the return hose and reconnect it, but in doing so succeeded in making the hole in the tank where it goes in, much bigger, now the source of a chronic leak, as the stain indicates.
My question is whether anyone has any experience, advice, etc. regarding joining this return hose to a T-connector on the Vent hose, just above where it connects to the tank? In that way, I could seal the hole that was punched into the tank, eliminating this leak source.
Many thanks
Bob Pullen
S/V Seanorita
Yucatan
 

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Jake N Eggs

Jake N Eggs

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Jun 2, 2011
347
Hunter H33 Port Credit Harbour, ON.
The fuel return should ideally be extended down into the tank so that it is submerged in the fuel. You have a clean out in the top of the tank. You could drill a bigger hole and install a brass bulk head fitting which would allow you to screw on a fitting to the bulkhead. The tank side of the fitting could have a hose pipe that extends into the tank.

Good luck.
 
Tim R.

Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
Jake N Eggs said:
The fuel return should ideally be extended down into the tank so that it is submerged in the fuel. ...
Click to expand
Why? None of my boats have ever had a return line submerged in the tank.

Otherwise, I agree with Jake and you should install a new fitting from the inside.
 
bria46

bria46

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Jan 15, 2011
286
Oday 272 Waukegan, IL, Sarasota, FL
By boats fuel tank used a return line does not drop down into tank either.
 
Dan Hill

Dan Hill

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Dec 16, 2006
353
Hunter 25.5 Cayuga Lake, NY
The only advantage of the return being tubed to the bottom of the tank would be to cut down on foaming, which diesel fuel can do. I don't think your system returns that much flow so I wouldn't be concerned there. Like another member stated, use your clean-out opening and install a bulkhead fitting that will give you a standard thread internally. Easy Peasy Repair!
 
Johnb

Johnb

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Jan 22, 2008
1,461
Hunter 37-cutter Richmond CA
My understanding is the return line should go to the bottom of the tank to avoid entraining air bubbles into the fuel as would occur if it was dropping back in. Please correct me if wrong.

I guess it needs to go back into the tank so you don't get warmed fuel recirculating as would be if it was just teed back into the engine feed line?
 
Maine Sail

Maine Sail

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Feb 6, 1998
11,704
Canadian Sailcraft 36T Casco Bay, ME
WrenchBender said:
The only advantage of the return being tubed to the bottom of the tank would be to cut down on foaming, which diesel fuel can do. I don't think your system returns that much flow so I wouldn't be concerned there. Like another member stated, use your clean-out opening and install a bulkhead fitting that will give you a standard thread internally. Easy Peasy Repair!
Click to expand
It can definitely do this but rarely is it a problem with the minimal return flows on small diesels.

We have a 72GPH polishing system that definitely needs the dip tube but I run a mini-polisher on customers boats which consists of the same Facet pump many of these boats have and even at full bore, through a 10 micron filter only, there is no foaming...
 
Alan

Alan

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Jun 2, 2004
4,174
Hunter 35.5 LI, NY
Your picture shows the vent hose coming off the tank and making almost a 180 degree turn as it heads back to your transome. At that point it would need to rise above the transome vent fitting before connecting to the thru hull vent thereby creating a fuel trap in the middle of the vent line. The vent line needs to be re-run to prevent any traps for fuel to remain in the line. Also, the return line appears to cracked and may need to be replaced.
 
Maine Sail

Maine Sail

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Feb 6, 1998
11,704
Canadian Sailcraft 36T Casco Bay, ME
Alan said:
Your picture shows the vent hose coming off the tank and making almost a 180 degree turn as it heads back to your transome. At that point it would need to rise above the transome vent fitting before connecting to the thru hull vent thereby creating a fuel trap in the middle of the vent line. The vent line needs to be re-run to prevent any traps for fuel to remain in the line. Also, the return line appears to cracked and may need to be replaced.
Click to expand
Yes that vent will be a burper... Also keep in mind that all fuel fittings should be double clamped..
 
Bob Pullen HC-33 1981

Bob Pullen HC-33 1981

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Aug 20, 2006
220
Hunter 33_77-83 Yucatan, Mexico
Thank you for all your replies.
Yes, I was aware of the vent line needing to be better positioned, and the cracked return line. Found a Moeller tank, identical to this one, 12 gal, with a metal return barbed connection added to the sending unit. Have ordered it and will have it installed with new vent line layout. Inspection port also found to be leaking at the thread. Tried new o-ring with silicon grease -- ok as a temp fix, but felt better in replacing tank.
thanks again
Bob
 
Jake N Eggs

Jake N Eggs

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Jun 2, 2011
347
Hunter H33 Port Credit Harbour, ON.
Tim R. said:
Why? None of my boats have ever had a return line submerged in the tank.

Otherwise, I agree with Jake and you should install a new fitting from the inside.
Click to expand
Tim,

It may not be a problem in a boat but if the fuel tank is below the engine some fuel systems can draw air back into the fuel lines trough the return. By having the return in the fuel this possibility is eliminated.
 
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