Water Pump Impeller Gasket – Fits Yamaha 40HP 50HP 2-Stroke (Replaces 663-44315-A0)

Product Details

This Water Pump Impeller Gasket is engineered for Yamaha 2-stroke outboard engines including 40 HP (1984–1994), 50 HP (1984–1987), 50 HP Pro Series (1987–1990), and P50 models (1995–1996). Designed as a direct-fit replacement, this gasket ensures reliable sealing between water pump components to maintain efficient cooling system performance.

This gasket replaces Yamaha OEM part number 663-44315-A0.

• Critical seal for water pump impeller housing
• Application-specific fitment for Yamaha 2-stroke outboards
• Recommended replacement during routine water pump service

Part Number Matrix

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

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Technical Specs

OEM Interchange

663-44315-A0

Application

Water pump impeller housing seal

Compatible Fuel Types

Gasoline

Engine Type

2-Stroke Outboard

What's in the Box

• 1 × Water Pump Impeller Gasket

Installation Notes

1. Disconnect the battery and lower unit, then remove the water pump housing to access the impeller and gasket.
2. Remove the old impeller gasket carefully; clean both mating surfaces thoroughly to remove debris, corrosion, or old sealant residue.
3. Inspect the impeller for wear or damage; replace if blades are cracked, torn, or deformed.
4. Position the new gasket dry onto the water pump base plate, aligning all bolt holes and water passages.
5. Install the impeller with the blade tips oriented in the correct rotation direction (consult service manual if unsure).
6. Apply a thin coat of marine grease to the impeller for easier installation and initial lubrication.
7. Carefully lower the pump housing over the impeller, ensuring blades fold smoothly without binding or tearing.
8. Torque housing bolts to manufacturer specification in a criss-cross pattern to ensure even gasket compression.
9. Reinstall the lower unit, reconnect the battery, and run the engine with water supply to verify proper flow and no leaks.

Troubleshooting & FAQ

How do I know when to replace the water pump gasket?

Replace the gasket any time you service or rebuild the water pump, or if you notice coolant leaks, overheating, or reduced water flow from the tell-tale. Regular inspection every 2–3 years or 200–300 hours is recommended for outboards in saltwater or heavy-use environments.

Can I reuse the old gasket?

No. Gaskets compress and conform to mating surfaces during use. Reusing an old gasket can result in improper sealing, leaks, and overheating. Always install a new gasket during water pump service.

Do I need sealant with this gasket?

In most cases, no additional sealant is required if surfaces are clean and flat. Consult your engine's service manual; some installations call for a thin film of water-resistant gasket sealant to aid sealing on rough or corroded surfaces.

Will this gasket fit other Yamaha models not listed?

This gasket is confirmed for the engines listed in the compatibility table. For unlisted models, cross-reference OEM part number 663-44315-A0 in your service manual or contact support with your engine serial number to verify fitment.

What causes water pump gaskets to fail?

Common causes include age-related hardening, improper torque during installation, corrosion of mating surfaces, running the engine dry (overheating), and debris in the cooling system. Regular maintenance and flushing help extend gasket life.

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 against 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

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.