A transfer pump includes a motor that attaches to a manifold with a motor mount that seals a top end of the manifold. The motor mount includes a tubular portion that extends into and threadably engages the manifold, to cooperatively define a channel therethrough. The manifold includes a plurality of inlet ports arranged generally in an annular pattern. An inner cylinder attaches to the manifold from below, disposed radially inward from the inlet ports, and a pressure cylinder attaches to the manifold, disposed radially outward from the inlet ports. The pressure cylinder includes a foot valve. A pump shaft extends from the motor, through the channel, and into the pressure cylinder. A large piston with a check valve is attached to the distal end of the shaft, and a small piston disposed in the inner cylinder is attached at an intermediate location.