30-803097T1 Transom Seal Bellows Kit for MerCruiser Alpha One Gen 1 | JLM Marine

Transom Seal Bellows Kit for MerCruiser Alpha One Gen 1 – OEM 30-803097T1

This comprehensive transom seal bellows kit is engineered for MerCruiser Alpha One Generation 1 stern drives. It provides a complete solution for rebuilding and repairing your drive system, including the transom seal assembly, water pump components, power trim cylinder seals, and a tilt/trim limiter sensor.

This kit directly replaces OEM part numbers 30-803097T1, 46-96148A8, 25-87400A2, and 805320A03, offering a cost-effective aftermarket alternative for MR/Alpha One sterndrive maintenance and overhaul projects.

• Complete rebuild kit with transom seal, gimbal bearing, bell housing gasket, water pump repair kit, power trim seals, and tilt/trim sensor
• Designed specifically for MerCruiser MR/Alpha One Generation 1 stern drives
• Comprehensive package eliminates the need for multiple separate purchases

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

Please check all parts clearly before ordering! Due to the large package size, return costs are very high. Verify compatibility before purchase.

• 1× R/MR / Alpha One Transom Seal Kit with Gimbal Bearing and Bell Housing Gasket (30-803097T1)
• 1× MR / Alpha One Water Pump Repair Kit (46-96148A5 / 60367A1 / 96148A8)
• 1× R/MR / Alpha One Power Trim Cylinder Seal Rebuild Kit (25-87400A2)
• 1× Tilt/Trim Limit Limiter Sender Sensor (805320A03)

Package parts are exactly as shown in the product images.

Installation Guide

1. Preparation: Disconnect the battery and raise the stern drive to the full up position. Clean the transom and gimbal housing thoroughly to remove old sealant and debris.
2. Remove Old Components: Detach the stern drive from the gimbal housing and remove the old transom seal, bellows, and gimbal bearing. Inspect all mounting surfaces for damage or corrosion.
3. Install Gimbal Bearing: Press the new gimbal bearing into the gimbal housing using a bearing installation tool. Ensure it is seated fully and squarely in the housing.
4. Install Bell Housing Gasket: Position the new bell housing gasket on the transom assembly. Apply a thin bead of marine-grade sealant if recommended by your service manual.
5. Install Transom Seal: Slide the new transom seal bellows onto the gimbal housing and secure with the provided clamps. Ensure the seal is not twisted and all clamps are tightened evenly.
6. Replace Water Pump Components: Disassemble the water pump housing and replace the impeller, gaskets, seals, and wear plate from the water pump repair kit. Lubricate the new impeller with glycerin or soapy water before installation.
7. Rebuild Power Trim Cylinders: Remove the trim cylinders and carefully disassemble them. Replace all O-rings, seals, and gaskets from the power trim rebuild kit, ensuring cleanliness to prevent contamination.
8. Install Tilt/Trim Sensor: Remove the old tilt/trim limiter sender sensor and install the new unit. Connect the wiring harness and verify secure mounting.
9. Reassemble Stern Drive: Carefully align and reattach the stern drive to the gimbal housing. Torque all mounting bolts to manufacturer specifications in the correct sequence.
10. Fill and Bleed: Refill the stern drive with the appropriate gear oil and bleed the power trim system. Check for leaks around all newly installed seals and gaskets.
11. Test Operation: Reconnect the battery and test trim/tilt functions in all directions. Run the engine in a test tank or on the water to verify proper water pump operation and check for leaks.
12. Final Inspection: After initial operation, recheck all fasteners and clamps for tightness. Inspect all seal areas for signs of leakage and address immediately if found.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my MerCruiser stern drive?
A: Verify that your stern drive is an Alpha One Generation 1 model. Check your service manual or the identification tag on your drive unit. Cross-reference the OEM part numbers (30-803097T1, 46-96148A8, etc.) with your existing components to ensure compatibility.

Q: What are the signs that my transom seal and bellows need replacement?
A: Common symptoms include water intrusion into the bilge area, visible cracks or tears in the bellows, gear oil leaking from the stern drive, or difficulty maintaining proper trim/tilt operation. Inspect bellows annually for deterioration.

Q: How often should I replace the water pump impeller and transom seals?
A: Water pump impellers should typically be replaced every 2-3 years or 200-300 hours of operation, whichever comes first. Transom seals and bellows should be inspected annually and replaced every 3-5 years or at the first sign of wear or damage.

Q: Can I install this kit myself or do I need a professional?
A: While experienced DIY mechanics with proper tools can perform this installation, it requires stern drive removal, precision alignment, and specific torque specifications. Professional installation is recommended to ensure safety and prevent costly damage from improper assembly.

Q: What's the difference between this aftermarket kit and the OEM version?
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.