I got the one from WalMart also, but I don't think it is a bilge pump, but rather just a pump that has a threaded piece. All bilge pumps I've seen don't have the threaded portion on it.
I actually tried a 1400 GPH bilge pump from Wal*Mart once, and couldn't even get it to pump the water over the edge of the boat into the sac. Went back to my 700 GPH aerator style pump til I got a 1100. Now I am fully automatic with Simers.