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

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

This transom seal repair kit provides all the necessary components to service MerCruiser Alpha One Gen 2 sterndrive units manufactured from 1991 and up. It is designed to meet or exceed OEM specifications for a reliable, long-lasting repair.

This kit serves as a direct replacement for MerCruiser part number 30-803099T1, Sierra 18-2600, and Quicksilver 803099T1, ensuring a precise fit and restoring the integrity of your vessel's transom assembly.

• Complete Repair Solution: Includes all required bellows, gaskets, and bearings for a comprehensive transom service.
• Direct Fitment: Engineered as a direct replacement for original components on Alpha One Gen 2 drives (1991+).
• Durable Construction: Made with high-quality rubber and metal components to withstand the harsh marine environment.

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 U-Joint Bellows Assembly (Replaces 816431A1)
• 1 x Alpha Exhaust Bellows (Replaces 8M0124227/18654A1)
• 1 x Gasket (Replaces 27-8M0091545/27-94996Q2)
• 1 x Bearing Assembly (Replaces 30-8M2010910/30-879194A01/30-862540A3)
• 1 x Hose-0.250 ID × 0.50 OD × 9.50 LG (Replaces 32-8M0062593/32-4172533)
• 1 x Water Hose (Replaces 32-8M0109048/32-8M0062309)
• 1 x Shift Cable Bellows Assembly (Replaces 74639A2)

Installation Guide

1. Disconnect the boat's battery before starting any work.
2. Remove the sterndrive unit from the transom assembly according to the manufacturer's service manual.
3. Carefully detach the old U-joint, exhaust, and shift cable bellows from both the bell housing and the transom.
4. Remove the old gimbal bearing. A slide hammer or specialized bearing puller tool is typically required for this step.
5. Thoroughly clean all mating surfaces to remove old sealant, corrosion, and gasket material.
6. Install the new gimbal bearing into the gimbal housing, ensuring it is properly aligned and fully seated.
7. Install the new shift cable bellow, ensuring a secure fit on both ends.
8. Apply a thin layer of bellows adhesive to the mounting surfaces and install the new exhaust and U-joint bellows. Secure them with clamps.
9. Install the new water intake hose and trim sender limit switch components if included.
10. Reinstall the sterndrive unit, carefully aligning the driveshaft with the gimbal bearing and engine coupler.
11. Tighten all fasteners to the specified torque. Reconnect all systems and check for leaks in a test tank or on the water.
12. Note: Professional installation is highly recommended for this procedure due to its complexity.

Troubleshooting & FAQ

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

A: This kit is specifically designed for all MerCruiser Alpha One Gen 2 sterndrives manufactured from 1991 onwards. To be certain, you can cross-reference your existing part numbers with those listed in our cross-reference table, such as MerCruiser 30-803099T1.

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

A: The most common indicators of failing bellows are visible cracks or perishing of the rubber, water intrusion into your boat's bilge, or a persistent roaring/grinding noise from the gimbal bearing, especially when turning the sterndrive.

Q: How often should I replace the bellows in this kit?

A: We recommend a thorough inspection of all bellows annually. A typical replacement interval is every 3-5 years, although this can be shorter if the boat is used frequently in saltwater or stored in harsh environmental conditions.

Q: Is this an OEM kit?

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.