Transom Seal Kit – Fits MerCruiser R/MR/Alpha One Gen I Stern Drives (Replaces 30-803098T1)

Transom Seal Kit – Fits MerCruiser R/MR/Alpha One Gen I Stern Drives (Replaces 30-803098T1)

This transom seal kit provides the essential components needed to service MerCruiser R, MR, and Alpha One Generation I stern drives produced from 1983 to 1991 (serial numbers 6225577 through 0D469858). It is engineered to meet or exceed OEM specifications for a reliable, leak-free seal.

This kit is a direct replacement for multiple industry part numbers, ensuring wide compatibility and a straightforward installation process for a complete transom reseal and gimbal bearing replacement job.

• Complete Service Kit: Includes all necessary bellows, gimbal bearing, gaskets, seals, and clamps for a full transom service.
• Direct Replacement: Designed to replace Mercury Marine P/N 30-803098T1 and other equivalent aftermarket parts without modification.
• Durable Construction: Made with high-quality rubber, plastic, 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 Heavy Duty Gimbal Bearing (Replaces 18-2100 / 30-60794A4)
• 1 x U-Joint Bellows (Replaces 18-2751 / 60932A4)
• 1 x Shift Cable Bellows (Replaces 18-2753-1 or 18-2753-2 / 74639)
• 1 x Exhaust Tube (Replaces 18-2760 / 78458A1) Note: This exhaust tube uses a single hose clamp on the transom side, which may result in a louder exhaust sound than the OEM dual-clamp setup.
• 1 x Water Intake Hose, 3/4" (Replaces 18-3601 / 32-32461)
• 1 x Water Intake Hose, 5/8" (Replaces 18-3602 / 32-41725-33)
• 1 x Outdrive Mounting Gasket Kit (Replaces 18-2743 / 27-94996-2)
• 2 x Bell Housing Gasket (Replaces 18-2840 / 27-35982)
• 1 x O-Ring (Replaces 18-7153 / 25-25439)
• 1 x O-Ring (Replaces 18-7117 / 25-35027)
• 1 x O-Ring (Replaces 18-7170 / 25-33504)
• 2 x Hose Clamp (Replaces 18-7310)
• 1 x Hose Clamp (Replaces 18-7312)
• 1 x Bellows Clamp (Replaces 18-7321 / 54-38863)

Installation Guide

1. Safety First: Disconnect the boat's battery before starting any work.
2. Remove Drive: Carefully detach and remove the MerCruiser stern drive unit according to the manufacturer's service manual.
3. Disassemble Transom Components: Remove the old bellows (U-joint, shift, and exhaust), gimbal bearing, and water hoses from the transom housing.
4. Clean Surfaces: Thoroughly clean all mounting surfaces on the transom and bell housing, removing any old gasket material or sealant.
5. Install Bearing: Use a gimbal bearing driver tool to properly install the new heavy-duty bearing into the gimbal housing.
6. Install Bellows: Install the new U-joint, shift cable, and exhaust bellows. Ensure they are correctly seated and secure all connections with the provided clamps.
7. Install Hoses and Gaskets: Fit the new water intake hoses and place the new gaskets and O-rings in their designated positions. Use appropriate marine-grade adhesive where required.
8. Reinstall Drive: Carefully reinstall the stern drive unit, ensuring proper alignment of the driveshaft and shift cable.
9. Final Checks: Reconnect the battery. Once in the water, check for any leaks around the transom assembly and test the drive for proper shifting and operation.

Troubleshooting & FAQ

How do I confirm this kit fits my MerCruiser stern drive?
This kit is compatible with MerCruiser R, MR, and Alpha One Generation I models from 1983 to 1991. To ensure a perfect match, verify your drive's serial number falls within the range of 6225577 to 0D469858 for sterndrives or 6216687 to 0D469858 for transom assemblies.

What is the difference between this kit's exhaust setup and the original OEM part?
The exhaust tube in this kit is designed for a single hose clamp on the transom side, which is a common aftermarket configuration. This may result in a slightly louder exhaust noise compared to the original dual-clamp OEM setup, but does not affect performance.

What are the signs that my transom seal kit needs to be replaced?
Common signs of failure include water leaking into the bilge area through the transom, a roaring or grinding noise from the gimbal bearing when turning the wheel, or visible cracks and deterioration in the U-joint or shift bellows.

Is everything I need for the job included in this kit?
This kit provides a comprehensive set of bellows, the gimbal bearing, gaskets, O-rings, and clamps needed for a typical transom service. You will still need appropriate marine-grade sealant/adhesive and standard mechanic's tools for installation.

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.