Diesel Fueling Question

Sep 6, 2020
26
Catalina 315 74 Barrington, RI
Hi all!

I have a 2021 Catalina 315, and I'm not clear on the best way to fill it with diesel. Probably a stupid question, but I'm not confident I'm fully filling the tank at each fuel-up.

While pumping, I listen for a change in sound from the fuel fill line, but I often don't hear any change and then see a little fuel start to spill out of the fuel vent line. After this point (and after wiping up the little spill), I can continue to add a bit more to the fuel fill line, without further vent line spilling. So a few questions:

1) when the vent line spills, does that guarantee the tank is full and I should stop? After that point am I simply filling the fuel line, not the fuel tank?
2) why don't I hear a sound change prior to the vent line spill? Am I pumping too fast, too slow, something else?

Thanks in advance!
Anthony
 

Tom J

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Sep 30, 2008
2,005
Catalina 310 Quincy, MA
We find it best to fill the diesel tank slowly. One of us will monitor the vent, with an absorbent pad at the ready, and let the one on the pump know when the air flow from the vent increases. Rather then risk a fuel spill, we would settle for an almost full tank instead of a topped off tank. The warning whistle looks like a good idea, but I have never tried one.
Some marinas make the filling process difficult, with their high pressure pumps with the big nozzles. If I fill the tank too quickly, the filler hose will overflow, so care must be taken to avoid this. In the end, these pumps can make filling the tank a longer process than normal.
 

RoyS

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Jun 3, 2012
1,216
Hunter 33 Steamboat Wharf, Hull, MA
Should not be fuel in the vent line. Vent hose should raise up immediately after exiting the tank. From there it should run horizontally as high as possible until it turns down to the hull vent fitting. If there is fuel trapped in your vent line it will take forever to fill your tank. Easily fixed.
 
Feb 21, 2013
3,791
Hunter 46 Point Richmond, CA
Ditto Tom J.......have absorbent pad at the vent outlet and deck fill. Fill slowly to avoid the risk of diesel fuel burping out the vent. I fill from a 2.5 gallon container with a button that stops fuel flow when I release my thumb.
 
May 24, 2004
6,799
CC 30 South Florida
Fuel tank vent should not be obstructed by any device including a tank whistle. We track our fuel burn and when we pull up to the pump we have a very good idea of how much it is going to take. We'll usually pump freely until we reach one gallon to go and then slowly continue to add until we feel the fuel coming up the vent. Filling to the brim has never been our goal, filling it to nearly full works for us and if we know we are going to need additional fuel we will carry it in fuel cans.
 
Jul 7, 2004
8,025
Hunter 30T Cheney, KS
Interesting. I assumed everyone had a gauge. Mine is on the top of the tank with a sight hole thru the laz flooring.
 

Tom J

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Sep 30, 2008
2,005
Catalina 310 Quincy, MA
Interesting. I assumed everyone had a gauge. Mine is on the top of the tank with a sight hole thru the laz flooring.
Well, yeah, I have a fuel gauge, but I can't see it while I am filling the tank. As Benny mentioned, I usually have a rough idea how much fuel I need, and if a dock attendant is at the pump, I'll ask him to let me know when I am getting close.
 
Feb 21, 2013
3,791
Hunter 46 Point Richmond, CA
Also have a fuel gauge in the cockpit but cannot see it when fueling AND since I am just topping off the fuel tank monitoring the gauge is not helpful so I ⁸listen for the sound when it gets close to full and vent to avoid burping out of it.
 
Last edited:
May 17, 2004
3,483
Beneteau Oceanis 37 LE Havre de Grace
I also just pump slowly and listen, and try to know beforehand about how much to expect. Too often this requires managing the dock hands, answering questions like “you know it’s going pretty slow, are you sure you’re pushing the handle all the way?”
 
  • Ha
Likes: Tom J
Oct 2, 2008
3,586
Pearson/ 530 Strafford, NH
I added a whistle to my vent hose which emits a sound during the filling process. It changes pitch when full and I still can get a burp from the vent which I catch with an overflow bottle. I don’t know if you can find those anymore.