Universal Marine Primer Bulb 10mm 3/8in One-Way Petrol Fuel Line MMS-1643
MMS-1643
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10mm / 3/8in Marine Primer Bulb
One-Way Hand Primer for Low-Pressure Petrol Fuel Lines
Aftermarket in-line primer bulb for compatible 10mm (3/8in inside-diameter) marine petrol hose. Squeezing the bulb draws fuel from the tank and pushes it towards the engine, helping fill an empty low-pressure line and external filter after service or storage. Internal check valves maintain the intended flow direction.
Key Features
- ✔ 10mm (3/8in) hose connections
- ✔ Integral one-way check valves
- ✔ Hand priming after filter or fuel-line service
- ✔ Reinforced bulb intended to resist vacuum collapse
- ✔ Aftermarket replacement; clamps sold separately
Technical Specs
| Part type | In-line hand primer bulb |
| Hose size | 10mm / 3/8in inside diameter |
| Flow control | Two internal one-way valves |
| Application | Low-pressure marine petrol supply line |
| Fuel statement | Supplier states ethanol-blend compatibility |
| SKU | MMS-1643 |
Compatibility / Fitment Guide
| Verification Point | Required Match | Not Suitable / Check First |
|---|---|---|
| Hose bore | Fuel hose is marked 10mm or 3/8in ID and fits the bulb tails without stretching, looseness or adapters. | Not a direct fit for 6mm, 8mm, 5/16in or other hose sizes. Measure hose ID, not outside diameter. |
| System position | Installed in the external low-pressure supply line between tank and engine, in the position permitted by the engine manufacturer. | Never install on the pressurised EFI rail, injection side, return line, oil line or inside an engine cover unless specifically approved. |
| Flow direction | Arrow on bulb points from the fuel tank towards the engine; hose routing avoids kinks and allows the bulb to be operated. | A reversed bulb will resist priming and can starve the engine. |
| Fuel | Petrol and ethanol blend are within the bulb supplier's rating and the hose/clamps are rated for the same fuel. | Do not assume compatibility with diesel, biodiesel, methanol-rich fuel, aviation fuel or non-fuel fluids. |
| Engine demand | The engine manufacturer specifies a 3/8in supply line and the bulb does not create unacceptable restriction at full fuel demand. | Horsepower alone is not a fitment rule; high-output, multi-engine and long-run systems require a flow/restriction check. |
| Connections | Marine fuel-rated hose is secured with correctly sized smooth-band stainless clamps and every joint passes a leak/air-ingress test. | Do not use damaged hose, oversized worm clamps that cut the hose, cable ties or sealant on barbed connections. |
Part Number Cross Reference
| 4Boats / supplier SKU | MMS-1643 |
| Connection description | 10mm / 3/8in hose-tail primer bulb |
| Supply type | Aftermarket universal-style replacement |
No OEM part-number equivalence is claimed. Compare the physical size, flow arrow and engine fuel-system requirements.
Frequently Asked Questions
Will it fit every outboard?
No. It fits compatible low-pressure petrol systems using 10mm/3/8in ID hose and adequate flow capacity.
Which way does it install?
The moulded arrow must point from the tank towards the engine.
Are clamps included?
No. Use correctly sized marine fuel-hose clamps suitable for the hose construction.
Why does the bulb not become firm?
Possible causes include reversed installation, an empty tank, open vent, leaking connector/hose, stuck check valve, filter leak or another air entry. Do not run the engine until fuel leakage and the cause are resolved.
When should it be replaced?
Replace if hard, cracked, swollen, sticky, leaking, slow to recover after squeezing, or unable to hold prime after the rest of the system has been checked.
Safety: Work in a ventilated area with ignition sources removed. After installation, prime slowly, inspect every joint for fuel and air leaks, and stop immediately if odour, wetness or abnormal bulb deformation appears.
For the products under £150 the shipping is £6.99.
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