Attwood Sahara S500 Automatic Bilge Pump 12V 500GPH 19mm Outlet
mms-1051
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Attwood Sahara S500 Automatic Bilge Pump
12V | 500 GPH open flow | integrated float switch
A compact automatic bilge pump combining a 12-volt pump and mercury-free caged float switch in one housing. It is intended for a correctly sized 19 mm discharge installation with protected wiring and clear access for inspection.
Key Features
- Automatic pump with integral mercury-free float switch
- 500 GPH nominal open flow
- 390 GPH stated at 1 m (3.3 ft) head
- 19 mm (3/4 in) discharge outlet
- 914 mm of 16 AWG tinned-copper lead wire
- Removable strainer base for service access
Technical Specs
| Supply | 12V DC |
| Current draw | 1.5 A stated |
| Open flow | 500 GPH (approx. 1,893 L/h) |
| Flow at 1 m head | 390 GPH stated |
| Outlet | 19 mm (3/4 in) hose |
| Dimensions | 140 × 82 × 102 mm |
| Lead wire | 914 mm, 16 AWG tinned copper |
| 4Boats SKU | mms-1051 |
Compatibility / Fitment Guide
Fitment is based on electrical supply, outlet plumbing, available bilge space and the vessel’s required pumping capacity — not simply on boat length.
| Electrical | 12V DC negative-ground systems only. Protect the positive feed with the fuse specified for the exact Attwood model and place the fuse close to the power source; use marine-grade connections above the normal bilge-water level. |
| Discharge plumbing | Requires 19 mm (3/4 in) smooth-bore bilge hose. Route continuously upward to an above-waterline through-hull where possible; avoid sags, crushed hose and tight elbows. Prevent back-siphoning as the boat heels or is loaded. |
| Mounting space | Allow at least 140 × 82 × 102 mm plus hose-bend and wiring clearance. Mount the strainer level at the lowest practical collection point, with the float free from cables, debris and structure. |
| Capacity selection | Use the stated 390 GPH at 1 m head as the more realistic comparison where that head applies. Larger boats, long hose runs or emergency dewatering may require additional/higher-capacity pumps. |
| Not a substitute for | A manually operable backup, high-water alarm, drainage maintenance or emergency damage-control equipment. |
Part Number Cross Reference
| Attwood model family | Sahara S500 automatic |
| Legacy retail reference commonly associated | 4505-7 — verify label on supplied pump |
| Current Mk2 family | 5505 series — different generation; compare outlet and mounting before substitution |
| 4Boats SKU | mms-1051 |
Use the identification label on the actual pump for wiring/fuse instructions. Do not assume every S500 generation has identical fittings or current draw.
Frequently Asked Questions
Will it run automatically?
Yes, when correctly wired and when rising water lifts the integral float.
Can it be the only bilge pump?
Pump quantity and capacity must be selected for the vessel and operating area; a single 500 GPH unit is not automatically adequate.
Can I reduce the outlet hose size?
No. A smaller or restrictive hose reduces flow and can overload the installation.
How should it be tested?
Add clean water to the bilge and confirm automatic start, discharge, shut-off and absence of backflow. Test regularly.
Bilge pumps do not prevent sinking. Keep seacocks, hoses, wiring, batteries and alarms maintained and investigate any recurring water ingress.
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