Fuel Pump Diaphragm Kit – Mercruiser/OMC Outboard (Replaces 155278A1, 55278A1)

$10.99 $17.00

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Fuel Pump Diaphragm Kit – Mercruiser/OMC Outboard (Replaces 155278A1, 55278A1) is backordered and will ship as soon as it is back in stock.

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Delivery and Shipping

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If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This Fuel Pump Diaphragm Kit is designed for a variety of Mercruiser and OMC outboard engines, specifically servicing 2- and 3-cylinder models from 40 to 150 HP produced up to the 1980s. It provides an essential refresh for your engine's fuel pump to restore performance and reliability.

This kit provides a direct interchange for Mercruiser part numbers 155278A1 and 55278A1, as well as OMC part numbers 0508426, 0509395, 0982240, 0985602, and 0985603.

Installation: Engine-mounted
Fuel Type: Compatible with gasoline
Key Component: Replaces the original manufacturer's diaphragm in the fuel pump

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number
Mercruiser	155278A1
Mercruiser	55278A1
OMC	0508426
OMC	0509395
OMC	0982240
OMC	0985602
OMC	0985603

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercruiser/OMC owners, this diaphragm kit fits a range of classic 2-stroke and 3-stroke outboards. Verify your model and year to ensure proper fitment.

Brand	Model	Rated HP	Stroke	Years	Notes
Mercruiser	1150				Compatible
Mercruiser	1350				Compatible
Mercruiser	1400				Compatible
Mercruiser	1500				Compatible
Mercruiser	400 (2 cyl)	40	2-Stroke	up to 1983	Compatible
Mercruiser	402 (2 cyl)	40	2-Stroke	up to 1983	Compatible
Mercruiser	40 (2 cyl)	40	2-Stroke	up to 1983	Compatible
Mercruiser	650 (3 cyl)	65	3-Stroke	1972–1976	Compatible

Technical Specs

Product Type: Fuel Pump Diaphragm Kit
Installation: Engine-mounted
Fuel Type: Gasoline
Dimensions: 5.13 in x 4.0 in x 1.13 in
Weight: 0.02 kg (0.04 lb)
Other Technical Attributes: Replaces original manufacturer's diaphragm in fuel pump

Installation Notes

Disconnect the battery and relieve any pressure from the fuel system.
Carefully disconnect the fuel inlet and outlet lines from the fuel pump, noting their positions.
Remove the mounting bolts securing the fuel pump to the engine block and detach the pump.
Disassemble the fuel pump housing by removing the screws to access the old diaphragm.
Remove the old diaphragm, taking note of the orientation of any associated springs or seals.
Thoroughly clean the mounting surfaces of the pump housing, ensuring no debris remains.
Install the new diaphragm from the kit, making sure it is properly seated and aligned.
Reassemble the pump housing and tighten the screws evenly to the manufacturer's recommended torque.
Reinstall the fuel pump onto the engine and tighten the mounting bolts.
Reconnect the fuel lines to the correct ports.
Reconnect the battery, prime the fuel system according to your engine's procedure, and check for any leaks before starting the engine.

Troubleshooting & FAQ

How do I know if my fuel pump diaphragm has failed?

Common signs of a failing fuel pump diaphragm include engine hesitation, stalling at low speeds, poor acceleration, rough idling, or visible fuel leaks from the fuel pump housing.

Is this kit compatible with my specific engine year?

This kit fits a wide range of Mercruiser and OMC models, primarily those manufactured up to the 1980s. Please review the "Engine & Model Compatibility" table and cross-reference your specific model and part number to ensure a correct match.

Can I replace just the diaphragm, or do I need a whole new pump?

If the pump housing, check valves, and other components are in good condition, replacing only the diaphragm with this kit can be a highly cost-effective repair to restore your fuel pump's function.

What is the recommended replacement interval for this part?

There is no strict replacement interval for a fuel pump diaphragm. It should be inspected during regular engine service for signs of stiffness, cracking, or deformation, especially on older engines. Replace it as a preventative measure if you suspect it is becoming brittle.

OEM vs. Aftermarket?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

Shipping speed & cost

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

Warranty & returns

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

Safety & Important Info

Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement, not an OEM component.
Professional installation is recommended for safety and performance.

About Sea Sierra

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Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.

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