663-44323-00 Water Pump Wear Plate for Yamaha 25J 25Q 30DE 30DMH 40N 40H 50D 55ED 55ET 55B | JLM Marine

Water Pump Wear Plate – Fits Yamaha 2-Stroke 25–55 HP Outboards (1984–1996)

This aftermarket water pump wear plate is engineered for Yamaha 2-stroke outboard motors ranging from 25 HP to 55 HP. It provides a precise replacement for models including the 25J, 25Q, 30DE, 30DMH, 40N, 40H, 50D, 55ED, 55ET, and 55B series produced between 1984 and 1996. Designed to restore proper cooling system function, this wear plate ensures reliable water flow and protects your impeller from premature wear.

This component directly replaces Yamaha OEM 663-44323-00, as well as aftermarket equivalents Sierra 18-3436 and Mercury Marine 81420M, offering broad cross-brand compatibility for service flexibility.

• Restores efficient water pump operation in Yamaha 2-stroke outboards
• Direct fit for 25–55 HP models across multiple series (J, Q, DE, DMH, N, H, D, ED, ET, B)
• Compatible with engines manufactured from 1984 to 1996

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Yamaha owners, here's a guide to help you identify your engine's serial/model: Yamaha Serial Number Guide. You can also review exploded diagrams to verify part numbers: Yamaha Parts Diagrams & Catalog.

Technical Specifications

Package Contents

• 1x Impeller Wear Plate (663-44323-00)

Installation Guide

1. Disconnect the fuel line and remove the engine cowling to access the lower unit. Drain the gear oil completely before proceeding.
2. Separate the lower unit from the midsection by removing the mounting bolts and shift linkage. Handle the shift rod carefully to avoid bending.
3. Locate the water pump housing on top of the lower unit gearcase. Remove the housing bolts and lift off the housing assembly.
4. Carefully remove the old impeller and wear plate. Inspect the pump housing and drive shaft for scoring or corrosion.
5. Clean all mating surfaces thoroughly using a gasket scraper and solvent. Ensure no debris or old gasket material remains.
6. Position the new wear plate onto the pump base, aligning all bolt holes and water passages correctly.
7. Lubricate the new impeller with water pump grease and install it with blades oriented in the correct rotation direction. Ensure the drive key engages properly.
8. Reinstall the water pump housing with a new gasket, torquing bolts evenly in a cross pattern to manufacturer specifications.
9. Reattach the lower unit to the midsection, reconnecting the shift linkage and ensuring proper gear engagement.
10. Refill the lower unit with the correct grade and quantity of gear oil. Check for leaks at the drain and vent screws.
11. Reinstall the engine cowling and reconnect the fuel line. Start the engine in a test tank or on-water and verify strong water flow from the telltale port.
12. Monitor engine temperature during the first run to confirm proper cooling system operation.

Troubleshooting & FAQ

Q: How do I confirm this wear plate fits my specific Yamaha outboard?
A: Cross-reference your engine's model and year with the compatibility table above. Verify your original part number matches 663-44323-00, Sierra 18-3436, or Mercury Marine 81420M. If your model is listed but the part doesn't physically match, do not install it.

Q: How often should I replace the water pump wear plate?
A: Replace the wear plate whenever you service the water pump impeller—typically every 2–3 years or 200–300 hours of operation. Always inspect for excessive wear, grooves, or corrosion during routine maintenance.

Q: What are the signs that my wear plate has failed?
A: Symptoms include weak or no water flow from the telltale, engine overheating, steam from the cowling, or visible damage to the impeller blades. Inspect the wear plate for deep grooves, cracks, or warping.

Q: Can I reuse the old wear plate if it looks okay?
A: It's not recommended. Even minor surface wear reduces impeller efficiency and can lead to premature failure. Always replace the wear plate during impeller service for optimal cooling performance.

Q: Will this aftermarket wear plate perform the same as the Yamaha OEM part?
A: Yes, this wear plate is manufactured to OEM specifications using comparable materials and tolerances. It provides equivalent fit, durability, and cooling performance at a more competitive price point.

Q: Is this an OEM part or an aftermarket replacement?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.