Straight Screw Plug Kit – Fits Yamaha 40HP-300HP (Replaces 688-45341, 90340-08002-00, 90430-08020)

Product Details

This Straight Screw Plug Kit is designed for Yamaha outboard engines ranging from 40HP to 300HP. It services most but not all engines in this horsepower range, making it essential to buy by part number rather than engine horsepower alone. This comprehensive drain plug kit ensures reliable lower unit maintenance across a wide range of Yamaha models.

This kit directly replaces OEM part numbers 688-45341, 90340-08002-00, and 90430-08020, providing a cost-effective aftermarket solution for lower unit servicing.

• Complete drain plug assembly with gaskets included
• Suitable for routine lower unit oil changes and maintenance
• Application-critical: always verify part number against your engine before purchase

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

Product Type

Straight Screw Plug Kit

Primary Application

Lower unit drain and fill service

Compatibility

Yamaha outboards 40HP–300HP (verify part number)

Kit Components

Drain plug, screw plug, and gaskets

What's in the Box

• 1 × Lower Unit Drain Plug (688-45341)
• 1 × Straight Screw Plug (90340-08002)
• 2 × Lower Unit Oil Drain Gasket (90430-08020)

Installation Notes

1. Position the outboard upright and allow the lower unit to drain completely if performing an oil change.
2. Remove the old drain plug(s) and inspect threads for damage or corrosion.
3. Clean the drain hole area thoroughly to remove old gasket material and debris.
4. Install a new gasket onto the drain plug. Do not reuse old gaskets.
5. Thread the drain plug by hand first to avoid cross-threading.
6. Tighten to manufacturer-specified torque using a calibrated torque wrench.
7. Refill the lower unit with the correct type and quantity of gear oil per your service manual.
8. Check for leaks after installation and during the first few hours of operation.

Troubleshooting & FAQ

How do I know if this kit fits my Yamaha outboard?

Cross-reference the OEM part numbers (688-45341, 90340-08002-00, 90430-08020) with your engine's parts diagram or service manual. Do not rely solely on horsepower rating, as some engines in the 40–300HP range may use different plugs.

Can I reuse the old gaskets?

No. Always replace gaskets during lower unit service to ensure a proper seal and prevent leaks. This kit includes two new gaskets.

What torque setting should I use for the drain plugs?

Refer to your Yamaha service manual for the exact torque specification. Over-tightening can strip threads or crack the lower unit housing; under-tightening may cause leaks.

How often should I replace the drain plugs and gaskets?

Gaskets should be replaced at every lower unit oil change. Drain plugs should be inspected each time and replaced if threads are damaged, corroded, or if the magnetic tip (if applicable) is excessively worn.

What are signs that my lower unit drain plug is failing?

Visible gear oil leaks around the plug, difficulty removing or installing the plug, stripped threads, or metal shavings on the magnetic tip beyond normal accumulation all indicate replacement is needed.

Is there a difference between the two plugs in this kit?

Yes. The kit includes one lower unit drain plug (688-45341) and one straight screw plug (90340-08002). Each serves a specific location on the lower unit. Install each in its correct position as shown in your service manual.

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.