Hi Paul, You're a prince for doing the calcs, thanks! >4 gpm is a lot of flow. That is a worst case, and not required if it gets us into trouble on self-prime. The rated flow is 2GPM for a single Shurflo. I don't know what it will actually be with any significant suction head, certainly less. However, I really need to make the transfer system operate near the 2 GPM, else it will take too long to move fuel. And I don't want to get involved with auto-shutdown complexity to protect against overfilling a tank. Is the pressure drop linear with flow rate? E.g., how do I estimate the values for 2GPM or less? >7.1 psi for 5/8" ID hose. Would it be too much trouble to give me the formulae you used? Then I will be able to understand the power laws for the various parameters. This reveals another gap in my knowledge. 7.1 psi is equivalent to 16.4 feet of water. I thought the self-prime spec (8-ft in this case) was another way of saying pump will self prime up to 3.5psi of negative suction pressure. Is this correct? My intuition is clanging - the equalivent water head values look ridiculous (e.g., 50-ft water vs. 21.8psi). >Lower the pumps if you possibly can. Unless I'm completely off the road on the above heads, we have no choice but to install 4 pumps down at the 4 hull tanks. >I see Cap'n Wil has put in his two cents worth. With the info above you're >almost up to a nickel. Chuckle. But the advice is actually priceless, in that I haven't found anybody yet in NZ who has the engineering in hand. I went to our nearest library, 75km south, looking for tech references. The only book even close to this field is one on Hydraulic design (which I already own :-) Many thanks, Steve ------------------------------------------------ Stephen C. Darden Email: darden@xtra.co.nz Adagio Marine Ltd. Fax: 649/4037-213 P.O. Box 161 Voice: 649/4037-801 Russell NEW ZEALAND