Transom Seal Repair Kit – Fits MerCruiser Alpha One Generation II (Replaces 803099T1)
Transom Seal Repair Kit – Fits MerCruiser Alpha One Generation II (Replaces 803099T1) 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 Generation II (...
Product Details
This Transom Seal Repair Kit – Fits MerCruiser Alpha One Generation II provides all necessary components to reseal the transom assembly on MerCruiser Alpha One Gen II sterndrive units manufactured between 1991–1997 (serial range 0D469859-0K999999). It is designed to replace worn or damaged bellows, bearings, and gaskets to prevent water leaks and protect critical drivetrain components.
This kit serves as a direct replacement for Mercury/Quicksilver part number 30-803099T1 and interchanges with Sierra parts 18-8206-1 (Greasable) and 18-8218 (Sealed).
- Installs at the bell housing and transom interface.
- Includes essential U-joint, exhaust, and shift cable bellows.
- Complete kit for a comprehensive transom service and reseal.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Mercury/Quicksilver | 30-803099T1 | |
| Sierra | 18-8206-1 | Greasable |
| Sierra | 18-8218 | Sealed |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For MerCruiser applications, verify that your sterndrive unit is an Alpha One Generation II and that its serial number falls within the specified range for a correct fit.
| Brand | Model | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| MerCruiser | Alpha One Gen II | 4-Stroke | 1991–1997 | 30-803099T1 | Serial range: 0D469859-0K999999 |
Technical Specs
- Product Type
- Transom Seal Repair Kit
- Installation
- Bell housing/transom interface
- Connection
- Mechanical interface with bell housing and transom
- Housing Material
- Rubber bellows, stainless steel clamps, brass/metal fittings
- Housing Color
- Black (bellows)
- Fitting Type
- Multiple bellows with clamp fittings
- Thread Size
- Multiple (varies by component)
- Warranty
- 1 year (Mercury Marine/Quicksilver products)
- Other Technical Attributes
- Complete transom seal repair/reseal kit for Alpha One Gen II stern drives with exhaust bellows
What’s in the Box
- 1 x U-Joint Bellows Assembly (Replaces 816431A1)
- 1 x Exhaust Bellows Assembly (Replaces 18654A1/8M0124227)
- 1 x Bearing Assembly (Replaces 30-862540A3/30-879194A01)
- 1 x Shift Cable Bellows Assembly (Replaces 74639A2)
- 1 x Water Hose (Replaces 32-4172533/32-8M0062309)
- 1 x Alpha Outdrive Mounting Gasket Kit (Replaces 27-94996Q2)
- 1 x Gasket (Replaces 27-8M0091545)
- 1 x Hose - .250 ID x .50 OD x 9.50 LG (Replaces 32-8M0062593)
- 1 x Hose Water (Replaces 32-8M0109048)
Installation Notes
- Disconnect the battery and secure the vessel before beginning work. Trim the sterndrive to the full "up" or "trailer" position.
- Remove the sterndrive unit from the bell housing according to the manufacturer's service manual.
- Detach the old exhaust, U-joint, and shift cable bellows from the transom and bell housing, cutting them if necessary.
- Remove the old gimbal bearing from the transom assembly using a slide hammer or bearing puller.
- Thoroughly clean all mating surfaces, removing old sealant, rust, and debris.
- Install the new gimbal bearing using an appropriate bearing driver until it is fully seated.
- Fit the new shift cable, U-joint, and exhaust bellows, ensuring they are correctly oriented and seated.
- Secure all new bellows with the supplied clamps, tightening to the torque specified in your service manual.
- Install the new water hose and all gaskets from the kit.
- Reinstall the sterndrive, carefully aligning the U-joint splines and shift cable. Torque all fasteners to spec.
- After reassembly, check for proper shift operation and inspect for water leaks once the vessel is in the water.
Troubleshooting & FAQ
How do I know if this kit fits my MerCruiser?
This kit is specifically for MerCruiser Alpha One Generation II sterndrives produced from 1991 to 1997. The most reliable way to confirm fitment is by checking your drive's serial number. It must be within the range of 0D469859 to 0K999999.
What are the signs my transom seal needs replacing?
Common symptoms of failing transom seals include water entering the bilge area, a roaring or grinding noise from the gimbal bearing (especially when turning), or visible cracking, holes, or deterioration on the rubber bellows.
Is the gimbal bearing in this kit greasable?
This kit includes a sealed gimbal bearing that is pre-lubricated for its service life, as per modern OEM standards. It does not have a grease fitting and does not require periodic greasing.
Can I replace just one bellow instead of the whole kit?
While it is technically possible, it is strongly recommended to replace all bellows, the gimbal bearing, and gaskets at the same time. These components wear at a similar rate, and the labor involved is nearly identical. Replacing the full kit prevents a near-future failure of another component.
What is the difference between the greasable and sealed Sierra replacements?
The greasable version (18-8206-1) includes a gimbal bearing that can be periodically greased, while the sealed version (18-8218) has a permanently sealed bearing that requires no maintenance, similar to the one in this kit. The choice depends on user preference for maintenance.
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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