Transom Bellows Repair Kit – Fits MerCruiser Alpha One Generation 2 (Replaces 30-803099T1, GLM 21960, Sierra 18-8206)

$319.99

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Transom Bellows Repair Kit – Fits MerCruiser Alpha One Generation 2 (Replaces 30-803099T1, GLM 21960, Sierra 18-8206) is backordered and will ship as soon as it is back in stock.

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This MerCruiser Alpha 1 Gen 2 Transom Bellows Repair Kit is designed for the comprehensive service of MerCruiser Alpha One Generation 2 stern drives manufactured from 1991 and up (serial numbers 0D469859 and higher). It provides all the essential components to restore the seal and function of the transom assembly.

It serves as a direct replacement for Mercury part number 30-803099T1 and interchanges with aftermarket references GLM 21960 and Sierra 18-8206.

Designed for outboard stern drive installations.
Constructed with marine-grade neoprene and stainless steel for resistance to water, oil, and fuel.
Includes U-Joint, Exhaust, and Shift Cable bellows, gimbal bearing, gaskets, and hoses for a complete installation.

Part Number Matrix

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

Brand	Part Number
Mercury	30-803099T1 / 803099T1
GLM	21960
Sierra	18-8206

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For MerCruiser applications, verify your engine’s serial number falls within the specified ranges to ensure correct fitment.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
MerCruiser	Alpha One Gen 2	All	Both	1991–1995	30-803099T1	Serial numbers: 0D469859 through 0F679999
MerCruiser	Alpha One Gen 2	All	Both	1996–1997	30-803099T1	Serial numbers: 0F680000 through 0K999999
MerCruiser	Alpha One Gen 2	All	Both	1998 and up	30-803099T1	Serial numbers: 0L100040 and up

Technical Specs

Product Type: Transom Bellows Repair Kit
Installation: Outboard Stern Drive
Connection: Transom Mount
Housing Material: Neoprene (Bellows), Stainless Steel (Clamps)
Housing Color: Black
Dimensions: 13.9 × 8.4 × 6.3 inches (353.1 × 213.4 × 160 mm) [package dimensions]
Weight: 5.00 lbs (2.27 kg)
Fitting Type: Clamp-style
Other Technical Attributes: Marine-grade materials resistant to water, oil, and fuel

What’s in the Box

1 × U-Joint Bellows Assembly (816431A1)
1 × Exhaust Bellows Assembly (18654A1/8M0124227)
1 × Bearing Assembly (30-862540A3/30-879194A01/30-8M2010910)
1 × Shift Cable Bellows Assembly (74639A2)
1 × Water Hose (32-4172533/32-8M0062309/32-8M0109048)
1 × Alpha Outdrive Mounting Gasket Kit (27-94996Q2/27-8M0091545)

Installation Notes

Disconnect the boat's battery and safely remove the stern drive unit from the transom assembly.
Carefully cut and remove the old U-joint, exhaust, and shift cable bellows. Note their orientation.
Remove the old gimbal bearing. Thoroughly clean all mounting surfaces and bell housing of any old sealant or debris.
Install the new gimbal bearing and the outdrive mounting gasket kit onto the transom.
Fit the new shift cable bellows, U-joint bellows, and exhaust bellows, ensuring each is properly seated.
Secure all new bellows with the provided stainless steel clamps, tightening them to manufacturer specifications.
Reinstall the stern drive unit, reattach all connections, and test for proper function and leaks in the water.

Troubleshooting & FAQ

How do I confirm this kit fits my MerCruiser drive?

This kit is specifically for Alpha One Generation 2 stern drives (1991 and newer). The most reliable way to confirm fitment is by checking your drive's serial number. It must be 0D469859 or higher. Refer to the compatibility table for specific ranges.

What are the signs that my transom bellows need to be replaced?

Common signs of failure include visible cracks, splits, or perishing of the rubber. The most critical symptom is finding water inside the boat around the transom or bell housing, which indicates a leak in the U-joint bellows.

Is the gimbal bearing always included in these kits?

Yes, this is a comprehensive repair kit that includes the gimbal bearing assembly (OEM ref 30-862540A3), alongside all necessary bellows, gaskets, and water hose for a complete service.

How often should I replace my transom bellows?

As a preventative maintenance item, it is recommended to inspect bellows annually for any signs of wear or cracking. A full replacement is advised every 3-5 years, depending on usage (saltwater vs. freshwater) and storage conditions.

OEM vs. Aftermarket?

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.

Shipping speed & cost?

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

Warranty & returns?

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.

Safety & Important Info

Verify images/specifications vs 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.

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