Hi Wil, >If you use this size hose, with a maximum flow rate of 4 gpm, you can forget >piping losses. Please see Paul's post and my reply. I may be off the road relating his pressure estimates to the self-prime spec, but the numbers I got imply there's no way these pumps will self-prime through 40-ft of 5/8" hose. Something doesn't add up here. >Few pump manufacturers provide complete pump curves. If you are lucky, you >get a flow rate shown at different discharge pressures, but this assumes a >flooded suction, and in most cases, a closed loop. Got it. >Pumps that can pull high vacuums are described as "positive displacement >pumps" and even the best of those can not lift water by suction more than >34-ft+/-. Does that mean a perfect pump can't overcome 1 atmosphere (1 bar = 33.456 ft of water)? >Anything that breaks the sealing surfaces of these valves will cause the >pump to malfunction -- anything! Right. But I'm sure particle size is a factor (three diaphragms, all somewhat resilient). E.g., a 1 micron particle probably has little effect. >Install a coumpound gauge My ignorance abounds - what is a compound gauge? >When you are done, you'll be a PUMP EXPERT -- for that pump. Thanks for the experiment brief. First I think I'll do the easy thing, which is to measure flow rate as function of suction head, and verify self-prime performance with no head on pressure side. That will tell me if my case is hopeless. >Only if you don't have junk in the tank that can get through the mesh. The >Walbro has a 15-micron steel mesh on its suction, and they still require a >real filter. If I understand that comment correctly, I'm beginning to wonder if there is any practical way to do the transfer/polishing function with a single central filter manifold. I.e., I sure don't want to have to install a Racor FG500 between each tank and the tank's local near-flooded pump. (I always thought my fall back method would be to replace the single central transfer pump with 4 pumps - one at each tank). >I don't know why you need 2-gpm, much less 4-gpm. The flow rate is only required for fuel transfer. The common supply to all engines is gravity feed from daytank (please description below). >An advantage of the Walbro is that it is a piston pump without any >connecting rods, etc. The piston is metal and is much less subject to >failure because of junk than a diaphragm pump. The Walbro sounds like a better design. Would they be suitable for the fuel transfer job? I researched the Walbro web site, but there is no technical data there. >If we start now, I could make it in little more than a year, but >I guess we'd need to design a fuel system for the transportation first. Chuckle! You should plan to come down here for the America's Cup so you can do some NZ cruising with us! But first we have to make this fuel system work.... Many thanks, Steve Adagio Fuel System Design ------------------------- 0. Requirements - transfer fuel between any of hull tanks and daytank. At least allow "ping pong" polishing between any pair of tanks. Minimize weight of fuel hose, couplings, valves. Reliability: Eight hour operation after failure of transfer pump function. Operable via manual transfer pump in event of total electrics failure. Bottom line goal - nothing but quality fuel ever goes into daytank, thence to any consumer, and only a vindictive God can disable our ability to generate onboard electricity. 1. Four integral hull tanks, one central wingdeck level daytank, which gravity feeds two Yanmars, one genset, one diesel boiler. 2. One fuel transfer and polishing pump (the Shurflo 8000 series with diesel elastomers). 3. There is only one each fuel line connecting the 4 hull tanks to the central transfer manifold - this supports "ping pong" polishing. To allow closed-loop polishing I added a second hose to the nearest hull tank. 4. Fuel can be transfered between any pair of the 5 tanks. This function is accomplished by 5 input-manifold valves, 5 output-manifold valves. 5. The transfer system is just the following in plumbing sequence: - 5 valve input manifold - RCI purifier - GCF F1 - transfer pump (serves both transfer and polishing) - 5 valve output manifold 6. To meet my goal of bullet-proof reliability, the "transfer pump" function is actually 3 parallel pumps (though only one pump is needed to make the system work): - Shurflo #1 - Shurflo spare (might as well have hot spare plumbed in, can also double transfer rate) - Whale manual bilge pump/diesel elastomers - absolute requirement for backup - which adds 6 more pump selector valves My problem - basically that tanks are below DWL, while daytank is on wing deck, the only possible gravity feed location. Second I want all the controls and serviceable bits (pump, filters) laid out on a chest level easy access panel (above one workbench). Result is the transfer pump has to deal with a 6 to 7-ft suction head, and we all know pumps want to push, not suck. Secondary problem - I prefer to have filters on suction side for 2 reasons: to avoid emulsification, and to protect the diaphragm pumps from debris. My guess is that this goal isn't feasible due to static pressure induced by the filters. Another alternative to address the suction head problem - I could substitute an Oberdorfer gear pump for the single Shurflo. Spec'd to self-prime to 20-ft (when new, degrades with wear). But these don't want to be run dry (needing a failure prone check valve on the suction), are big, heavy, expensive, noisy and more difficult/expensive to service. (I can buy 4 Shurflo tank-level pumps for price of one Oberdorfer, which also yields 4x redundancy). My intuition is telling me this tank-pump scheme may be required, though I hate the complexity, dead-weight double hose lengths, long, heavy supply wires (or worse, relays). ------------------------------------------------ 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