Transom Seal Repair Kit – Fits MerCruiser Alpha One Gen 2 Sterndrive (Replaces 30-803099T1)

Transom Seal Repair Kit – Fits MerCruiser Alpha One Gen 2 Sterndrive (Replaces 30-803099T1)

This complete transom seal repair kit fits MerCruiser Alpha One Generation 2 sterndrives manufactured from 1991 and up, with serial numbers 0D469859 and higher. It contains all necessary components to seal the transom opening, including bellows, gaskets, a greasable gimbal bearing, and seals.

Directly replaces Mercury/Quicksilver part number 30-803099T1 / 803099T1, Sierra 18-8206-1, GLM 21960, and Mallory 9-72904.

• Fits MerCruiser Alpha One Gen 2 (1991+, S/N 0D469859+).
• Includes a greasable gimbal bearing and a hinge pin tool for installation.
• Engineered as a direct replacement for OEM part 30-803099T1.

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 Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

• 1 x Drive Shaft Bellows (816431A1)
• 1 x Exhaust Bellows Assembly (18654A1)
• 1 x Shift Cable Bellows Assembly (74639A2)
• 1 x Water Hose 3/4" (32-41725)
• 1 x Gimbal Bearing (30-60792A4)
• 1 x Gasket Kit (27-94996T2)
• 1 x Hinge Pin Tool (91-78310/9178310)
• 4 x O-Rings

Installation Guide

1. Disconnect the battery and trim the sterndrive to the full "up" position.
2. Remove the drive unit by detaching the hydraulic trim rams and the six main mounting nuts.
3. Carefully remove the old exhaust, shift, and drive shaft bellows from the transom assembly.
4. Extract the old gimbal bearing using a slide hammer or bearing puller tool.
5. Clean all mating surfaces on the bell housing and transom assembly thoroughly.
6. Install the new greasable gimbal bearing, ensuring the grease hole is correctly aligned for future maintenance.
7. Install the new shift cable bellows, followed by the exhaust bellows and drive shaft bellows. Secure all clamps tightly.
8. Install the new water intake hose and all required gaskets from the kit.
9. Reinstall the sterndrive unit, ensuring proper alignment of the driveshaft and U-joints.
10. Torque all nuts and bolts to the manufacturer's specified values.
11. Reconnect the hydraulic rams and the battery.
12. Before operating in water, check for leaks and verify proper shifting and steering function.

Troubleshooting & FAQ

How do I confirm this kit fits my MerCruiser sterndrive?
This kit is designed for MerCruiser Alpha One Generation 2 sterndrives from 1991 and newer, specifically those with serial numbers 0D469859 and higher. Please check your drive's serial number, typically located on the side of the upper housing, to confirm compatibility.

How often should the transom bellows be replaced?
For optimal performance and to prevent water intrusion, we recommend inspecting the bellows annually for cracks, stiffness, or signs of wear. The recommended replacement interval is every two years, even if no visible damage is present.

What are the signs of a failing transom seal?
Common symptoms include water collecting in the bilge area, a stiff or noisy gimbal bearing when turning the wheel, or visible cracks and decay on the rubber bellows. Any of these signs indicate an urgent need for inspection and repair.

Is the included gimbal bearing the greasable type?
Yes, the kit includes a greasable-style gimbal bearing (part number 30-60792A4), which allows for easier maintenance and longer service life when lubricated properly.

OEM vs. Aftermarket?
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.

How fast do you ship and how much does it cost?
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.

What is your warranty and return policy?
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.