Transom Seal Kit – Fits MerCruiser Bravo I II III (Replaces 30-803100T1, 8M0095485, 18-8219)

Product Details

This 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 comprehensive bellow reseal repair kit provides all the critical seals, gaskets, and hardware needed to restore transom assembly integrity and prevent water intrusion.

Direct replacement for MerCruiser part numbers 30-803100T1, 8M0095485, and aftermarket equivalent 18-8219.

• Complete reseal solution with bellows, gimbal bearing, gaskets, and stainless clamps
• Fits all Bravo I, II, and III configurations from 1982 onward
• Includes U-joint, exhaust, and shift bellows for full transom service

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Technical Specs

Application

MerCruiser Bravo I/II/III Sterndrive

OEM Reference

30-803100T1, 8M0095485

U-joint Bellows Part

86840A05

Exhaust Bellows Parts

78458A1, 18654A1

Shift Bellows Part

74639A2

Gimbal Bearing Part

30-862540A3

Water Hose Part

32-43437

Mounting Gasket & O-rings Part

16755Q1

Clamp Type

Stainless steel bellows clamps

What's in the Box

This kit is not listed in the package include field, so contents are derived from the eBay description as a supplement:

• 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 Notes

1. Disconnect battery and remove drive unit per manufacturer service manual.
2. Inspect the gimbal housing and transom plate for corrosion or damage before installing new components.
3. Remove old bellows and clamps, taking care not to damage mounting surfaces.
4. Press out the old gimbal bearing using a suitable bearing puller or driver.
5. Clean all mounting surfaces thoroughly and apply marine-grade corrosion inhibitor.
6. Install the new gimbal bearing, ensuring it seats fully and squarely in the housing.
7. Fit the U-joint, exhaust, and shift bellows over their respective shafts, positioning clamps loosely.
8. Install mounting gasket and O-rings in correct grooves; do not over-torque fasteners.
9. Attach water hose and secure with clamps at both ends.
10. Tighten all bellows clamps evenly, working from the center outward to avoid pinching.
11. Reinstall drive unit, verify alignment, and torque all transom mounting bolts to specification.
12. Reconnect battery, perform a water test, and inspect all seals for leaks under normal operating conditions.

Troubleshooting & FAQ

How do I know if my bellows need replacement?

Inspect for cracks, splits, brittleness, or water intrusion in the bilge. A failed bellow can allow water into the boat or damage internal components. Replace all bellows as a set during transom service to avoid future failures.

Can I reuse the old clamps?

Reusing clamps is not recommended. Stainless clamps lose tension over time and may not seal properly after removal. This kit includes new clamps for reliable clamping force.

Do I need special tools to replace the gimbal bearing?

Yes, a bearing puller and driver set (or hydraulic press) are recommended for safe removal and installation. Improper installation can damage the bearing or housing.

Is this kit compatible with Alpha One drives?

No. This kit is specifically designed for Bravo I, II, and III drives. Alpha One drives require a different bellows and bearing configuration.

What's the difference between this and the OEM kit?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

How often should I replace transom bellows?

Inspect bellows annually and replace every 3–5 years or sooner if cracking, splitting, or water intrusion is detected. Frequent high-RPM use or saltwater operation may accelerate wear.

How fast will this ship, and what does it cost?

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

What if this doesn't fit or I have a problem?

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

Will this kit work on a Bravo X drive?

Bravo X drives share the same transom assembly as Bravo I, II, and III. Verify your serial number and compare component part numbers before ordering to ensure full compatibility.

Safety & Important Info

• Verify images/specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.
• This is an aftermarket replacement, not an OEM component.
• Professional installation is recommended for safety and performance.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.