Overview

The Attwood Marine 4505ST1 is a Sahara S500 automatic bilge pump for 12V systems with a Quicksilver connector, rated at 500 GPH at open flow and 350 GPH at 3.3 feet of head. It fits a 3/4 inch I.D. discharge hose and uses a built-in automatic switch, so it suits boats that need a compact pump with automatic operation already built in.

The housing is about 5-1/2 inches long, 3-1/4 inches wide, and 4 inches high, which helps when bilge space is limited. This pump is for clearing standing bilge water, not fuel, oil, or fast flooding from heavy weather or hull damage. The pump body is sealed and submersible, but the electrical connection still needs to stay out of the water during installation.

Key features

• 12V automatic bilge pump in the Sahara S500 class with a built-in switch and manual test knob
• 500 GPH open-flow rating and 350 GPH at 3.3 feet of head
• Quicksilver connector version for boats already rigged with that connector style
• Uses 3/4 inch I.D. hose and a 2 amp fuse for this pump model
• Compact body at about 5-1/2 x 3-1/4 x 4 inches for tighter bilge areas
• Mercury-free switch and 316 stainless steel motor shaft

Installation and fit

This pump is usually mounted on a flat pad at the lowest practical point in the bilge, with the outlet aimed toward the transom. For the best result, the discharge hose should rise steadily to the thru-hull rather than dipping along the way, and the float end of the pump should sit level with or slightly above the outlet end.

For replacement work, the main checkpoints are straightforward: confirm a 12V circuit, a 3/4 inch discharge line, room for the pump body, and a harness that matches the Quicksilver connector on this version. That connector detail matters on boats where keeping the existing rigging layout is preferable to reworking the bilge pump connection.

Use on board

This pump is a good match for runabouts, skiffs, bass boats, and other boats with a smaller bilge compartment and a 3/4 inch discharge setup. It also makes sense when you want automatic bilge protection in the 500 GPH range without adding a separate float switch assembly for the same basic job.