Overview

The Attwood Marine 4505-7 is an automatic 12V Sahara S500 bilge pump rated at 500 GPH at open flow and 350 GPH at 3.3 feet of head, with a 3/4 inch discharge outlet. It combines the pump and automatic switch in one body, which keeps installation simpler in tight bilge spaces and avoids the extra footprint of a separate float switch.

This is a practical fit for boats that need unattended bilge water removal while sitting at the dock, on a mooring, or between trips. It is meant to clear standing bilge water, not fuel, oil, or fast flooding from hull damage or heavy weather.

Key features

• Automatic pump with an integrated mercury-free switch, so the unit can cycle on when water rises without a separate float switch.
• 12V output rated at 500 GPH at open flow and 350 GPH at 3.3 feet of head, which gives a clearer picture of installed performance.
• Fits a 3/4 inch I.D. discharge hose, which matters when matching an existing hose run or thru-hull size.
• Uses 16-gauge tinned copper leads and calls for a 2 amp fuse, which helps when planning the wiring run and switch panel connection.
• Permanent-magnet motor, stainless steel shaft, steel-reinforced seal, and a strainer base that can be removed for cleaning.

Installation and setup

Mount the pump in the lowest flat part of the bilge with the outlet pointing toward the transom and the discharge nozzle kept level. The hose should rise steadily to the thru-hull without dips, since trapped water or air in the line can cause airlock and cut pumping performance.

The pump body is sealed and submersible, but the wire connections should stay out of the water and be sealed properly. For a standard helm-controlled circuit, install it with an inline fuse and an AUTO/OFF/MANUAL switch.

Compatibility and fit

This pump makes sense on 12V boats already set up for a 3/4 inch bilge discharge hose, especially where space is limited and a combined pump-and-switch layout is easier to place. It also works well as a secondary automatic pump in a stepped bilge, fish box sump, or other low point where you want backup water removal without adding another float switch.

Use on board

It suits owners who want a simple automatic bilge pump for runabouts, small center consoles, aluminum fishing boats, and sailboats with a modest bilge area. On larger boats, it is more often used as a secondary pump or for a smaller compartment rather than the main high-capacity bilge circuit.