Sizing Fuel Line for Pressure Drop

[Eric Johnson]

On the SB Marine website, Tony has a pressure drop article which results in a pressure drop of .4” HG for a 20 foot run of ½ inch fuel line. I am coming up with the same number, roughly. My boat is very similar to the example, ie about 20 feet, new build, Cummins 325 HP, 32 foot Holland.

I don’t understand why I should increase to 5/8 line over 15 feet per the article. If I am changing fuel filters at 10” HG, it is such a small fractional gain?? Maybe I am missing something, but with a 5/8 inch fuel line, the pressure drops in half, to .2” HG, so I only pick up .2” HG, .2/10=2%., seems minimal?

Maybe the base pressure with clean filters won’t be zero?, but even still, seems minimal percent gain?

Thanks in advance for any clarification.

Topic

[Tony Athens]

So why increase? .4″ Hg is nothing to worry about. And realize, that is at 60 GPH–What are you really flowing? If your tank lever in higher than the filters, then it will even be less.

Do you have actual “field measurements”, or we still on the “drawing board”….

The gist of this article is make owners aware of how “it all interacts” , not to make one go up in fuel line ID for no reason.

Tony

[Author]

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