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

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

This transom seal repair kit provides the essential components needed to service MerCruiser Alpha One Generation 2 sterndrives manufactured from 1991 to the present (serial numbers 0D469859 and up). It is engineered to meet or exceed original equipment specifications for a reliable, direct-fit replacement.

This assembly serves as a direct replacement for Mercury part number 30-803099T1, as well as aftermarket equivalents including Sierra 18-8206-1 and Mallory 9-72904.

• Installation Type: Direct OEM replacement requiring no modifications.
• Core Components: Includes marine-grade rubber bellows (U-joint, exhaust, drive shaft), water hose, seals, and a greasable gimbal bearing.
• Durability: Features stainless steel clamps for enhanced corrosion resistance in marine environments.

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 (18654A1/8M0124227)
• 1 x U-Joint Bellows (74639A2)
• 1 x Gimbal Bearing Assembly (30-862540A3/30-879194A01/30-8M2010910)
• 1 x Water Inlet Hose (32-4172533/32-8M0062309/32-8M0062593)
• 1 x Outer Seal Kit (27-94996Q2/27-8M0091545)

Installation Guide

1. Safety First: Before starting, disconnect the boat's battery and ensure the sterndrive is trimmed down completely.
2. Remove Sterndrive: Detach the sterndrive unit from the transom assembly according to the manufacturer's service manual.
3. Remove Old Components: Carefully cut and remove the old U-joint, exhaust, and drive shaft bellows. Note the orientation of clamps. Disconnect the old water hose.
4. Extract Gimbal Bearing: Use a slide hammer with a bearing puller attachment to remove the old gimbal bearing from the housing.
5. Clean Surfaces: Thoroughly clean all mounting surfaces on the transom housing and bell housing, removing any old sealant or debris.
6. Install New Bearing: Drive the new gimbal bearing into place using a suitable bearing installation tool until it is properly seated. Ensure the grease hole is correctly aligned.
7. Install Bellows: Install the new exhaust, U-joint, and drive shaft bellows. Apply adhesive and secure all clamps tightly.
8. Connect Water Hose: Attach the new water inlet hose to its connection points.
9. Replace Seals: Install the new gaskets and seals from the outer seal kit.
10. Reinstall Sterndrive: Re-mount the sterndrive unit, ensuring all components align correctly. Torque all fasteners to the specified values.
11. Final Check: Reconnect the battery. Once in the water, check for any leaks around the transom assembly.
12. Lubricate: Grease the new gimbal bearing through the grease fitting.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my Alpha One Gen 2 sterndrive?

A: This kit is designed for MerCruiser Alpha One Gen 2 models from 1991 to present. You must verify that your sterndrive's serial number is 0D469859 or higher to ensure compatibility.

Q: What are the common signs that my transom seals need replacing?

A: Key indicators include visible cracks or perishing on the rubber bellows, water collecting inside the bellows, a roaring or grinding noise from a worn gimbal bearing, or water leaking into the boat's bilge from the transom area.

Q: How often should bellows and gimbal bearings be inspected or replaced?

A: Bellows should be inspected annually for cracks, holes, or stiffness and typically replaced every 3-5 years, depending on usage and water conditions (saltwater vs. freshwater). The gimbal bearing should be checked for smoothness at the same time and replaced if it feels rough or noisy.

Q: OEM vs. Aftermarket?

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.