Power Steering Cylinder Kit – Fits Mercury MerCruiser Alpha & Bravo Stern Drives (Replaces 806034A2, 8M0149869)
Power Steering Cylinder Kit – Fits Mercury MerCruiser Alpha & Bravo Stern Drives (Replaces 806034A2, 8M0149869) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Power Steering Cylinder Kit – Fits Mercury MerCruiser Alpha & B...
Product Details
This is a high-quality aftermarket Power Steering Cylinder Kit – Fits Mercury MerCruiser Alpha & Bravo Stern Drives. It is designed for reliable performance in MerCruiser Alpha One and Bravo models, primarily from 1986 through 1993, restoring original steering function and feel.
It directly replaces Mercury OEM part numbers 806034A2, 8M0063381, 8M0149869, 8M0208403, 89645A15, and 89645A9.
- Features a robust no-feedback DHB (Dynamic Hydraulic Boost) cylinder/valve assembly for low steering feedback and improved handling.
- Engineered for direct replacement but requires specific mounting hardware and may need SAE adapter fittings for older hydraulic systems.
- Constructed from a durable blend of aluminum and stainless steel to resist corrosion in marine environments.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By |
|---|---|---|
| Mercury | 89645A9 | 89645A15 |
| Mercury | 89645A15 | 806034A2 |
| Mercury | 806034A2 | 8M0063381 |
| Mercury | 8M0063381 | 8M0149869 |
| Mercury | 8M0149869 | 8M0208403 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
Designed for specific MerCruiser stern drive models. Check your serial number and year to ensure a correct match.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| MerCruiser | 300 | 1984–1986 | 806034A2 | Multiple serial number ranges |
| MerCruiser | 320EFI [ALPHA] | 1988 | 806034A2 | Serial: 4320100AH |
| MerCruiser | 320EFI [BRAVO] | 1988–1989 | 806034A2 | Serial: 4320110AH, 4320110BH |
| MerCruiser | 530D [BRAVO] | 1988–1993 | 806034A2 | Multiple serial number ranges |
| MerCruiser | 636D [BRAVO] | 1988–1993 | 806034A2 | Multiple serial number ranges |
| MerCruiser | 642D [BRAVO] | 1990–1993 | 806034A2 | Multiple serial number ranges |
Technical Specs
- Product Type
- Power Steering Cylinder Kit / Actuator Assembly
- Installation
- Direct replacement; requires specific mounting hardware
- Connection
- Metric hydraulic fittings (requires SAE adapter fittings for older models)
- Housing Material
- Aluminum and stainless steel
- Housing Color
- Silver/metallic
- Dimensions
- 60.0" L x 22.0" W x 15.0" H
- Fitting Type
- Metric hydraulic fittings
- Other Technical Attributes
- No-feedback DHB (Dynamic Hydraulic Boost) cylinder/valve assembly design; Low steering feedback for improved handling
What’s in the Box
- 1 x Power Steering Cylinder Kit (806034A2/8M0063381/8M0149869/8M0208403)
Installation Notes
- Disconnect the battery and ensure the engine is off and cool.
- Position the stern drive in the full-tilt position for access. Support it securely.
- Place a drain pan under the hydraulic lines and carefully disconnect them from the old cylinder, keeping track of their positions.
- Unbolt and remove the old power steering cylinder assembly. Retain mounting hardware if it will be reused.
- Mount the new cylinder assembly, ensuring it is correctly aligned. Torque bolts to manufacturer specifications.
- Reconnect the hydraulic lines to the correct ports on the new cylinder. Ensure fittings are tight but not over-torqued.
- Refill the power steering fluid reservoir to the correct level with the recommended fluid type.
- Bleed the system by turning the wheel lock-to-lock several times until steering is smooth. Check for leaks.
- Reconnect the battery and test steering operation before use.
Troubleshooting & FAQ
How do I know if this cylinder fits my boat?
This cylinder is for MerCruiser Alpha One and Bravo stern drives, mainly from 1984–1993. Verify your engine model, year, and serial number against the compatibility table. The most reliable method is to match your existing part number to the numbers listed (e.g., 806034A2, 8M0149869).
What are the signs of a failing power steering cylinder?
Common symptoms include stiff or jerky steering, whining noises from the hydraulic pump, visible fluid leaks around the cylinder or lines, or a "drifting" feeling where the boat does not hold its course.
Do I need special tools to install this part?
Standard mechanic's tools, including a wrench set and torque wrench, are required. A line wrench for hydraulic fittings is highly recommended to prevent stripping. You will also need a method to safely support the stern drive.
This cylinder uses metric fittings. What if my boat has SAE fittings?
Many older MerCruiser models used SAE (inch) hydraulic fittings. You will need to purchase SAE-to-metric adapter fittings from a hydraulic supply store to connect your existing lines to this cylinder. Confirm your line sizes before purchasing adapters.
What is a DHB (Dynamic Hydraulic Boost) cylinder?
DHB is a "no-feedback" design that isolates the driver from prop torque and steering loads, resulting in lighter, smoother steering effort and improved handling, especially at higher speeds. This is an upgrade over older, feedback-style systems.
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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