Mark Savalla
Veteran Member
Installed new pump will not pump well. Lots uf air, do they need to be primed?
New fresh water pump
- Thread starter Mark Savalla
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Lou_tribal
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Heron
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Fill the system with your antifreeze mix .....Leave the expansion tank cap off, start and top off as the level goes down. You may need to "Burp" the hoses to clear the air bubble..
rochepoint
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A little confused, exactly which pump are we talking about......a pressure fresh water pump or a engine circulation pump?
Mark Savalla
Veteran Member
Fresh water pump
Maerin
Guru
Short answer: It depends.
On the type of pump. Most FW pumps are diaphragm on an eccentric shaft, so no priming needed. If it's (unlikely) a centrifugal, air in the impeller housing can create cavitation leading to no delivery. Depending on the design of the pump, some will self-prime, but it may take a while.
If, in fact it's a diaphragm pump, you probably have a leak on the inlet. Check the inlet fittings, most have an O-ring fitting, check it for debris on the mating surfaces, lube the O-ring with some silicone grease (NO VASELINE!). You DID replace all the O-rings on the connections, didn't you?? No side stresses on the fittings, they should fit easily. If it has an inline inlet strainer, check that the same, lube the mating surfaces with silicone grease (same NO VASELINE), and visually inspect for air ingress. If air bubbles show up in the clear window, you most likely have an air leak. You can have an air leak where no water will show. Some joints with an O-ring don't seal by compressing the O-ring during tightening, so drawing it into next week won't help. It seals by close tolerance fit inside a smooth circumference, so dirt can create a leak. Even a hair along the O-ring can be enough to create a leak path, so cleanliness is key. Don't ask the dog to hold the drop light.
Last edited:
Mark Savalla
Veteran Member
Hi folks thanks for all the suggestions. I'll make it as short as possible. I purchased a new pump, 4gpm, hooked it up, didn't work, checked breaker switch, wire off, hooked it up, pump ran but wouldn't pump, lots of air, check local area, discovered line going to exterior of hull where you hook up city water leaking. Disconnected that., checked again, same thing, lots of air little water. Checked accumulator, it was bad, I removed it because the specs on the pump did not require one. Ran again, same results. Called plumber, checked water tank and line. Line OK, tanks empty. I had filled them the week before and had not used them. Figured out the breaker must have been on, when the accumulator lost pressure, the pump kicked on, all water was pumped out through the crack in the external water hose line and water pumped overboard by bilge pump and then primary pump burned up or pressure switch gave out. Now the system without the external line and the accumulator and with water in the tank , the system works fine. I could not make this up. Thanks for all the valid suggestions.
