Lower Case Gasket – Fits Yamaha 9.9HP & 15HP Outboards (Replaces 683-45315-A0-00)

$5.89 $9.00

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Product Details

This aftermarket Lower Case Gasket is designed for a wide range of Yamaha 9.9HP and 15HP, 2-Stroke and 4-Stroke outboard engines. It provides a reliable, high-integrity seal for the engine's lower unit, preventing leaks and ensuring proper performance.

It serves as a direct interchange for Yamaha part numbers 683-45315-A0-00, 683-45315-A0, 683-45315-00-00, and is also cross-referenced with Sierra part 18-99152.

Installs on the engine lower unit housing to create a secure seal.
Constructed from a durable paper/composite material to resist oil and water.
Critical for maintaining the integrity of the engine's internal sealing system.

Part Number Matrix

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

Brand	Part Number
Yamaha	683-45315-A0-00
Yamaha	683-45315-A0
Yamaha	683-45315-00-00
Sierra	18-99152

Engine & Model Compatibility

Confirm your engine model and horsepower in the table below. It is critical to verify your specific OEM part number before ordering.

Brand	Model	Rated HP	Stroke	OEM Part No.	Notes
Yamaha	Various	9.9	2-Stroke & 4-Stroke	683-45315-A0-00	Also fits 15HP models
Yamaha	Various	15	2-Stroke & 4-Stroke	683-45315-A0-00

Technical Specs

Product Type: Lower Case Gasket / Packing
Installation: Engine Lower Unit
Housing Material: Paper / Composite
Housing Color: Green
Dimensions: 7.5" L x 11.0" W x 0.2" H
Weight: 50 g (0.11 lb)
Other Technical Attributes: Used for engine sealing system

What’s in the Box

1 x Packing, Lower Case (Replaces 683-45315-A0-00 / 683-45315-A0 / 683-45315-00-00)

Installation Notes

Generic installation process. Refer to your engine's official service manual for detailed instructions and torque specifications.

Disconnect the spark plug leads and battery for safety.
Position a drain pan under the lower unit and remove the gearcase oil drain and vent screws to drain the oil completely.
Remove the mounting bolts securing the lower unit to the engine's upper casing.
Carefully detach the lower unit from the engine. You may need to gently tap it with a rubber mallet to free it.
Remove the old lower case gasket and meticulously clean both mating surfaces of any old gasket material, sealant, or corrosion.
Position the new gasket correctly onto the lower unit.
Re-attach the lower unit, ensuring it aligns properly. Tighten the bolts in a crisscross pattern to the manufacturer's recommended torque.
Reinstall the gearcase drain and vent screws (using new washers if required) and refill with the correct type and amount of marine gear oil.

Troubleshooting & FAQ

How do I confirm this gasket fits my specific engine?

This gasket fits a wide variety of Yamaha 9.9HP and 15HP outboard models. The best way to ensure compatibility is to match the OEM part number 683-45315-A0-00 to the one listed in your engine's service manual or by inspecting your existing part.

What are the signs of a failing lower case gasket?

Common signs include visible oil leaks between the lower unit and the engine housing, or milky/creamy gear oil, which indicates water intrusion. A damaged gasket should be replaced whenever the lower unit is serviced.

Is any sealant required with this gasket?

Typically, this type of gasket is designed to be installed dry. However, always consult your motor's service manual, as some specific models may recommend a light application of a non-hardening sealant.

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 and 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.

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