Marine Fuel Water Separator Filter Head 1/4in NPT 11/16-16 MMS-4346
mms-4346
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Marine Fuel / Water Separator Head
1/4in NPT Ports | 11/16-16 Filter Thread | Aluminium
Compact aftermarket aluminium mounting head for external marine petrol fuel/water separator systems. The four-port layout allows the installer to choose inlet and outlet positions on the same or opposite sides; unused ports must be closed with the supplied plugs. It accepts the listed Mercury/Yamaha-pattern spin-on filters with an 11/16-16 centre thread.
Key Features
- ✔ Die-cast aluminium separator head
- ✔ Four selectable 1/4in NPT fuel ports
- ✔ Same-side or cross-head fuel routing
- ✔ Supplied with hose barbs and blanking plugs
- ✔ Accepts 11/16-16 marine spin-on filters
Technical Specs
| Material | Die-cast aluminium |
| Fuel ports | 4 x 1/4in NPT female |
| Filter thread | 11/16-16 |
| Supply | Head, barbs and plugs; filter not included |
| 4Boats SKU | MMS-4346 |
Compatibility / Fitment Guide
| Check | Required Match | Exclusion / Installation Note |
|---|---|---|
| Filter element | 11/16-16 centre thread and sealing-gasket diameter matching this head; examples include 35-809097, S3213/S3214, B32013 and Sierra 18-7919/18-7932/18-7928 families. | Not compatible with common 1in-14 spin-on elements. Cross-reference alone does not override physical thread/gasket checks. |
| Fuel-line ports | Selected fittings have 1/4in NPT male threads and barbs sized to the actual fuel hose. | Do not force 3/8in NPT, BSP or straight threads into the ports. Hose size and pipe-thread size are different measurements. |
| Flow routing | Tank supply enters an IN port and engine feed leaves an OUT port according to the cast markings; unused ports are fuel-tight plugged. | Do not route by appearance. Reversed or open ports can cause fuel starvation, air entry or leakage. |
| Fuel/application | External low-pressure marine petrol system using a compatible separator element and fuel-rated hose/fittings. | Not an under-cowl filter, high-pressure EFI component or diesel separator unless the complete filter system is specifically rated for that fuel and flow. |
| Mounting | Vertical, rigid mounting with access below to spin off the filter and room for any drain bowl; protected from spray, heat and ignition sources as required. | A clear collection bowl may be prohibited in enclosed/below-deck petrol spaces; use the element/bowl type required by the installation standard. |
| System capacity | Filter micron rating and flow capacity meet the engine manufacturer's requirements without excessive restriction. | Do not select only by engine brand or horsepower; verify required filtration, maximum flow and allowable suction restriction. |
Part Number Cross Reference
| Sierra bracket | 18-7853-1 |
| GLM / Mallory | 25000 / 9-37860 |
| MerCruiser references | 89876A3; 89876; 55481 |
| Yamaha reference | MAR-FLTHD-AL-12 (superseded in some catalogues) |
| 4Boats SKU | MMS-4346 |
This is an aftermarket replacement head. Cross-reference numbers identify the application family; they do not represent genuine OEM packaging.
Frequently Asked Questions
Is the spin-on filter included?
No. The listing is for the mounting head with fittings/plugs. Select a compatible 11/16-16 element separately.
Are the fuel ports 3/8in?
No. This head is specified with 1/4in NPT female ports. The supplied hose barb may fit a different hose ID; verify both dimensions.
Can inlet and outlet be on the same side?
Yes, if the cast IN/OUT routing is followed and all unused ports are correctly plugged.
Will it fit every Mercury or Yamaha?
No. It is an external universal-style system component. Confirm filter thread, port size, element rating, available space and engine fuel-flow requirements.
Installation note: Use fuel-rated hose, clamps and compatible thread sealant that does not contaminate the system. Prime and pressure/leak-test every joint before operating the engine.
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