Transom Seal Repair Kit – Fits MerCruiser Alpha One Gen 2 (Replaces 30-803099T1, 18-2600)
Transom Seal Repair Kit – Fits MerCruiser Alpha One Gen 2 (Replaces 30-803099T1, 18-2600) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Transom Seal Repair Kit – Fits MerCruiser Alpha One Gen 2 (Replaces...
Product Details
This complete Transom Seal Repair Kit is designed for MerCruiser Alpha One Gen 2 sterndrive units manufactured from 1991 and onward. It provides all the essential components needed to replace old, cracked, or leaking transom bellows and the gimbal bearing, restoring the integrity of your sterndrive system.
This kit serves as a direct replacement for MerCruiser part 30-803099T1, Sierra 18-2600, and Quicksilver 803099T1, ensuring a precise fit and function.
- Engineered as a direct replacement for all original components.
- Includes U-joint, exhaust, and shift cable bellows, plus gimbal bearing and gaskets.
- Connects the transom to the drive shaft and exhaust system.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| MerCruiser | 30-803099T1 / 803099T1 |
| Sierra | 18-2600 |
| Quicksilver | 803099T1 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For MerCruiser applications, this kit is specifically for Alpha One Generation 2 models from 1991 to present.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | Alpha One Gen 2 | Various | 4-Stroke | 1991–up | 30-803099T1 | Complete transom seal repair kit |
Technical Specs
- Product Type
- Transom Seal/Bellows Repair Kit
- Installation
- Direct replacement for original components
- Connection
- Transom to drive shaft and exhaust
- Housing Material
- Rubber/elastomer bellows with metal components
- Housing Color
- Black
- Dimensions
- Kit packaged dimensions: 353.1 × 213.4 × 160 mm (13.9 × 8.4 × 6.3 in)
- Weight
- 2.27 kg (5 lbs)
- Fitting Type
- Direct OEM fit
- Thread Size
- Various (matches OEM specifications)
- Other Technical Attributes
- Complete kit for transom seal repair
What’s in the Box
- 1 x U-Joint Bellows Assembly (816431A1)
- 1 x Alpha Exhaust Bellows (8M0124227/18654A1)
- 1 x Gasket (27-8M0091545/27-94996Q2)
- 1 x Bearing Assembly (30-8M2010910/30-879194A01/30-862540A3)
- 1 x Hose-0.250 ID × 0.50 OD × 9.50 LG (32-8M0062593/32-4172533)
- 1 x Water Hose (32-8M0109048/32-8M0062309)
- 1 x Shift Cable Bellows Assembly (74639A2)
Installation Notes
- Disconnect the vessel's battery and ensure the engine is off and cool.
- Remove the sterndrive unit according to the manufacturer's service manual to access the transom assembly.
- Carefully cut and remove the old U-joint, exhaust, and shift cable bellows.
- Extract the old gimbal bearing using a slide hammer and puller attachment.
- Thoroughly clean the bell housing and transom surfaces, removing all old sealant and debris.
- Install the new gimbal bearing using a bearing driver, ensuring it is squared and fully seated.
- Fit the new shift cable bellow first, followed by the U-joint and exhaust bellows, using the appropriate bellow adhesive.
- Secure all new bellows with the provided clamps and allow adhesive to cure as directed.
- Replace the water intake hose and associated gaskets.
- Reinstall the sterndrive unit, torquing all fasteners to OEM specifications.
- Reconnect the battery and perform a leak check in a controlled environment before returning to service.
Troubleshooting & FAQ
How do I know if my transom seals need replacing?
Common signs of failure include visible cracks or dry rot on the rubber bellows, water inside the bellows (check by turning the drive fully and inspecting), or a grinding/roaring noise from the gimbal bearing when turning the helm.
Is this kit compatible with an older Alpha One Gen 1 drive?
No, this kit is specifically for Alpha One Gen 2 sterndrives (1991 and newer). The components are not interchangeable with Gen 1 models.
What are the most common causes of premature bellow failure?
Failure is often caused by age, UV exposure, improper winterization, and marine growth. Extended time with the drive trimmed up can also stretch the bellows, accelerating wear.
How often should I replace my transom seals?
As a preventative maintenance item, it's recommended to inspect bellows annually and replace them every 5-7 years, or immediately if you notice any signs of wear, regardless of age.
Can I replace just one bellow instead of the whole kit?
While possible, it is strongly recommended to replace all the bellows, hoses, and the gimbal bearing at the same time. They wear at a similar rate, and the labor to access them is the same.
Are any special tools required for this job?
Yes, professional installation requires specific tools like a gimbal bearing puller/installer, a hinge pin tool, and a bellow expander tool. Bellow adhesive is also necessary.
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.
Payment & Security
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