30-803100T1 Transom Seal Kit for MerCruiser Bravo I II III | JLM Marine

Transom Seal Kit for MerCruiser Bravo I, II, III – Direct Replacement for 30-803100T1

This comprehensive transom seal kit is engineered for MerCruiser Bravo I, II, and III sterndrive applications from 1982 and up. Designed to meet or exceed OEM specifications, this complete reseal repair kit provides all the essential bellows, bearings, gaskets, and hardware needed to restore your transom assembly to peak performance.

Direct Replacement for: Mercury 30-803100T1, 8M0095485 | Sierra 18-8219. This aftermarket kit delivers OEM-grade quality at a competitive price, ensuring reliable protection against water intrusion and exhaust leaks.

• Complete reseal kit with U-joint bellows, exhaust bellows, shift bellows, gimbal bearing, water hose, and all necessary gaskets and clamps
• Stainless steel bellows clamps included for secure, corrosion-resistant installation
• Fits MerCruiser Bravo One, Bravo Two, and Bravo Three sterndrives (1982 & up)

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

This transom bellow reseal repair kit includes the following components:

• U-joint Bellows – #86840A05
• Exhaust Bellows – #78458A1 & 18654A1
• Shift Bellows – #74639A2
• Gimbal Bearing – #30-862540A3
• Water Hose – #32-43437
• Mounting Gasket & O-rings – #16755Q1
• Stainless Steel Bellows Clamps

Installation Guide

1. Disconnect the battery and ensure the engine is off and cool. Remove the drive unit from the transom assembly according to your MerCruiser service manual.
2. Inspect the transom plate and gimbal housing for corrosion, cracks, or damage. Clean all mating surfaces thoroughly and remove old gasket material.
3. Remove the old gimbal bearing using a bearing puller or press. Install the new gimbal bearing (#30-862540A3) with a bearing driver, ensuring it is fully seated and aligned.
4. Install the new mounting gasket and O-rings (#16755Q1) onto the gimbal housing. Apply a light coating of marine grease to the O-rings to aid installation.
5. Attach the U-joint bellows (#86840A05) to the gimbal housing and driveshaft yoke. Secure both ends with the supplied stainless steel clamps, ensuring they are tight and properly positioned in the grooves.
6. Install the exhaust bellows (#78458A1 & 18654A1) between the transom plate and drive unit. Route it carefully to avoid kinks or pinching, then secure with clamps.
7. Attach the shift bellows (#74639A2) over the shift cable assembly. Ensure it is fully seated on both ends and clamp securely.
8. Connect the water hose (#32-43437) to the fittings on the transom assembly and drive unit. Tighten clamps to prevent leaks.
9. Reinstall the drive unit onto the transom assembly, aligning the driveshaft and shift cable. Torque all mounting bolts to manufacturer specifications.
10. Inspect all bellows and connections for proper seating and clamp tightness. Verify that no bellows are twisted or pinched.
11. Reconnect the battery and perform a visual inspection before launching. Run the engine briefly on a hose or in the water to check for leaks or abnormal operation.
12. Test the steering, shift, and throttle operation before taking the boat underway. Monitor for leaks during the first few hours of use.

Troubleshooting & FAQ

Q: How do I know if my transom bellows need replacement?
A: Inspect bellows regularly for cracks, tears, dry rot, or water intrusion inside the bilge near the transom assembly. If you notice water leaking into the boat, exhaust fumes in the bilge, or visible damage to the rubber, replace the bellows immediately to prevent engine or transom damage.

Q: Can I replace just one bellows instead of the entire kit?
A: While individual bellows can be replaced, it is recommended to replace all bellows, gaskets, and the gimbal bearing together during a transom reseal. This ensures all components are fresh and reduces the likelihood of repeat service calls due to failure of other aging parts.

Q: How often should I replace the transom bellows and gimbal bearing?
A: Inspect bellows annually and replace them every 3–5 years or sooner if cracks or deterioration appear. Gimbal bearings should be replaced if you feel roughness, binding, or hear noise during steering, or as part of a comprehensive transom reseal every 5–7 years.

Q: Will this kit fit my Bravo drive if it was manufactured before 1982?
A: This kit is designed for MerCruiser Bravo I, II, and III drives from 1982 and up. If your drive is older or a different model (e.g., Alpha, R, MR), verify compatibility with your parts manual or contact our support team before purchasing.

Q: Do I need any special tools to install this transom seal kit?
A: You will need basic hand tools, a torque wrench, a bearing puller/driver set for the gimbal bearing, and marine grease. A service manual for your specific MerCruiser model is highly recommended for torque specifications and alignment procedures.

Q: What is the difference between OEM and aftermarket transom seal kits?
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.