Diesel fuel travel distance from tank to engine

[theglo]

Question!

I am installing a 20 gallon auxiliary diesel tank in the aft lazarette of my Dufour monohull. It will be about 17 feet away from my Perkins 4.236.

Will I have any difficulty or need to install an additional pump to feed fuel to the engine that distance or return diesel to the tank after it passes thru the engine?



BACK STORY.

I have 4 fuel tanks already on the boat totaling over 200 gallons. Last I used the boat in rough seas they sloshed around and clogged my filters causing lots of curse words and work the following morning when the engine wouldn't start.

I am using the boat again for a 3 week Bahammas trip shortly and do not have the ability to haul the boat to remove the current fuel tanks, cut inspection holes in them, clean them, and then remount.

I plan to eventually install a generator in the aft lazarette.

My interim fix for my fuel issue is to install the future generator's 20 gallon tank and then plumb that tank to my engine for this Bahammas trip. That 20 gallon plus a few 5 gallon jerry cans will do the job capacity wise. Then, once I return, I can haul the boat and fix the fuel issue correctly by repairing and cleaning the old tanks.

Thanks!

[rbk]

Distance will not be a problem but you also have to consider the height. If your pump has to lift the fuel 4-5 ft you may have issues. Mine pulls over 20 ft but the tank is a foot above the pump.

[tkeithlu]

Let's elaborate on rbk's answer.

Pumping fliuds over a distance is an issue of friction loss. Friction loss is a function of the length of the hose, the cross section of the hose, the volume being pumped, and the viscosity of the liquid. If you make the cross section of the hose big enough, any liquid can be sucked or pushed through any distance at any volume. Practically, that means that if you pipe the whole thing in 1/8" copper tubing, you may have a problem. If you use 1/2" copper tubing you will not.

The second issue is lift. You can't lift water with a pump above about 32 feet because it vaporizes at that vacuum. "Maximum lift" is directly proportional to density. Diesel has a density less than water, so it can be lifted farther. No problem for you there - your pump is not at the top of your mast.

The remaining possible problem is the pump itself. Can it lift enough fuel per minute to the height you do have? If the surface of the fuel is above, at, or nearly at the height of the pump, you'll be fine.

So, plumb it with a generous size of tubing, and go sailing.