Bearing Ball – Fits Mercury Outboard 135-300 HP & Stern Drive & Inboard (Replaces 30-88957T)

Product Details

This replacement Bearing Ball is designed for a wide range of Mercury Outboard engines from 135 to 300 HP (both 2-Stroke and 4-Stroke models) and various MerCruiser Stern Drive and Inboard models from 1983 to the present. It serves as a crucial component in the drive and transom assemblies, ensuring smooth operation.

This part is a direct replacement for multiple OEM and aftermarket part numbers, including Sierra 18-1155, GLM 21620, and Mallory 9-75114.

• Engineered for use on outboards between 110-250 HP.
• Meets or exceeds original equipment specifications for fit and performance.
• Package includes one essential bearing ball for a complete replacement.

Part Number Matrix

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

Engine & Model Compatibility

Confirm your engine model and year in the tables below to ensure proper fitment.

Mercury Outboard Applications: Fits various 2-stroke and 4-stroke models from 115 HP up to 300 HP. Please verify your specific model and serial number range.

MerCruiser Stern Drive & Inboard Applications: Compatible with numerous classic and modern MerCruiser drives, including Alpha One (Gen I & II), R/MR, and various inboard engine configurations.

Technical Specs

Product Type

Bearing Ball

Weight

0.43 kg (0.95 lbs)

Package Dimensions

11.0 cm L x 11.0 cm W x 5.0 cm H

Application Note

Used on outboards between 110-250 HP

What’s in the Box

• 1 x Bearing Ball (Replaces 30-88957T)

Installation Notes

1. Disconnect the battery and ensure the engine/drive system is secured and cannot start accidentally.
2. Consult your service manual to locate the specific housing containing the bearing ball (e.g., gimbal housing, gear case).
3. Disassemble the unit according to manufacturer procedures to access the old bearing.
4. Carefully remove the worn or damaged bearing. Clean the housing surface of any old grease, debris, or corrosion.
5. Lubricate the new bearing ball with marine-grade grease before installation.
6. Press the new bearing into place, ensuring it is properly seated and aligned. Do not use excessive force.
7. Reassemble all components in reverse order, tightening bolts to the specified torque values.
8. Once fully assembled, check for smooth movement and proper function before reconnecting the battery and testing on the water.

Troubleshooting & FAQ

Safety & Important Info

• Verify images and specifications against your original part before purchase. If anything differs—even if your model appears compatible—do not order.
• This is an aftermarket replacement part, not an original equipment manufacturer (OEM) component.
• Professional installation is strongly recommended for safety, performance, and to prevent damage to your marine engine.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world saltwater and freshwater conditions.
• Fast Global Fulfillment — With partners worldwide, we offer free standard delivery to most regions, typically arriving in 5–15 days.
• Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.