OK, I bought a 12 volt portable transfer pump to move water from a 55 gallon tank to a bucket. It has two places for hoses...an inlet and an outlet. Just to test it I put the inlet hose in a bucket full of water and attached another hose to the outlet fitting.  The inlet hose is about two feet long.  I attached it to my 12 volt fully charged deep cycle battery.  The motor runs and the impeller is turning but not getting much suction.  The pump is advertised as "self priming" but I don't think so.  I bought the thing on EBay and although listed as new it came with no instructions.

I've since read reviews about this pump (I know, hindsight!) and there are a lot of complaints about it not priming on it's own but no suggestions on how to prime it manually.  Can anyone tell me how to prime it?

If the pump has to be mounted above the water line of the tank, you can install a check valve (foot valve) on the end of the inlet feed hose. This will prevent the standing column of water, from draining back into the reservoir when the pump is shut off. The pump will not have to prime itself the next time it is started, and will run more efficiently.

If it were my system, I would install a check valve on the end of the inlet hose, sitting on the bottom of the tank. From there it would loop over the top of the tank to the pump, mounted at the same level as the bottom of the tank. This would provide a constant head pressure and prevent the hose from draining into the tank, if a slight inlet suction leak were to occure.

Mounting the tank with a bottom outlet directly to the pump will work, but if a leak occures, the tank will empty.

I figured out that pouring water down the inlet hose and immediatly putting the hose down in the bucket worked to prime the pump to get it going.

However I may need to try the other suggestions listed here once I use it on the actual water tank.

Thanks for all the help.