Hinge Pin Tool – Fits MerCruiser Alpha & Bravo (Replaces 91-78310, 18-9861)
Hinge Pin Tool – Fits MerCruiser Alpha & Bravo (Replaces 91-78310, 18-9861) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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Hinge Pin Tool – Fits MerCruiser Alpha & Bravo (Replaces 91-783...
Hinge Pin Tool – Fits MerCruiser Alpha & Bravo (Replaces 91-78310, 18-9861) is backordered and will ship as soon as it is back in stock.
Product Details
This specialty Hinge Pin Tool is designed for removing and installing the hinge pins on both port and starboard sides of MerCruiser sterndrive bell housings. It is compatible with a wide range of models, including Alpha One (Gen I & II), Bravo (I, II, & III), MC-1, R, and MR sterndrives, ensuring broad application for many boat repair and maintenance tasks.
It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Mercury 91-78310, Sierra 18-9861, GLM 90200, and Mallory 9-79805.
- Constructed from high-strength hardened steel for durability.
- Features a 12-point Allen style head for a secure fit on the hinge pin bolt.
- Engineered for manual use with a direct drive connection.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 91-78310 |
| Sierra | 18-9861 |
| GLM | 90200 |
| Mallory | 9-79805 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This tool fits a comprehensive range of Mercury MerCruiser sterndrive models. Please verify your specific drive model and serial number range where applicable.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | Alpha One Gen I | Various | Various | 1998 & Up | 91-78310 | Trim sender covers hinge pin |
| MerCruiser | Alpha One Gen II | Various | Various | 1998 & Up | 91-78310 | Trim sender covers hinge pin |
| MerCruiser | Bravo I | Various | Various | All | 91-78310 | Multiple serial ranges supported |
| MerCruiser | Bravo II | Various | Various | All | 91-78310 | Multiple serial ranges supported |
| MerCruiser | Bravo III | Various | Various | All | 91-78310 | Multiple serial ranges supported |
| MerCruiser | Bravo X One | Various | Various | 0M100001 & Up | 91-78310 | |
| MerCruiser | Bravo X Two | Various | Various | 0M100001 & Up | 91-78310 | |
| MerCruiser | Bravo X Three | Various | Various | 0M100001 & Up | 91-78310 | |
| MerCruiser | Bravo X Four S | Various | Various | All | 91-78310 | |
| MerCruiser | Bravo XR One | Various | Various | 0L914990 & Up | 91-78310 | |
| MerCruiser | Bravo XR Sport | Various | Various | All | 91-78310 | |
| MerCruiser | Bravo XR Sportmaster | Various | Various | 0M052945 & Up | 91-78310 | |
| MerCruiser | Bravo XR Three | Various | Various | All | 91-78310 | |
| MerCruiser | Bravo XZ One | Various | Various | All | 91-78310 | |
| MerCruiser | High Performance Transom | Various | Various | All | 91-78310 | |
| MerCruiser | Integrated Transom | Various | Various | All | 91-78310 | Multiple serial ranges supported |
| MerCruiser | MC-1 | Various | Various | All | 91-78310 | |
| MerCruiser | R | Various | Various | All | 91-78310 | |
| MerCruiser | MR | Various | Various | All | 91-78310 | |
| MerCruiser | Quicksilver Alpha One | Various | Various | All | 91-78310 |
Technical Specs
- Product Type
- Specialty Marine Service Tool
- Installation
- Manual
- Material
- Hardened Steel
- Tool Type
- 12-Point Allen Style
- Purpose
- Hinge Pin Removal/Installation
- Connection
- Direct Drive
- Other Technical Attributes
- Used to remove and install hinge pins on port and starboard sides of sterndrive bell housings
What’s in the Box
- 1 x Hinge Pin Tool (91-78310/18-9861/90200/9-79805)
Installation Notes
This tool is used on the hinge pin bolt to separate the gimbal housing from the gimbal ring. On most MerCruiser models, the trim and tilt sender covers the hinge pin access point and must be removed before you can use the tool. Once access is clear, the tool is used to properly remove and reinstall the pivot bolts on both the port and starboard sides of the bell housing.
Troubleshooting & FAQ
What is this tool specifically used for?
This tool is designed to remove and install the hinge pins that connect the sterndrive bell housing to the gimbal ring on MerCruiser drives. It features a 12-point head that correctly fits the hinge pin bolts.
Do I need to remove other parts to access the hinge pins?
Yes, in most applications, the trim and tilt sender unit is mounted over the hinge pin. You will need to remove the sender to gain access to the pin before using this tool.
How do I know if this tool fits my specific MerCruiser model?
This tool is compatible with Alpha One (Gen I & II), Bravo (I, II, III, and various X/XR models), MC-1, R, and MR sterndrives. Please consult the compatibility table on this page to confirm your specific model and year range.
What are the signs that my hinge pins need service or replacement?
Signs of failing hinge pins include excessive play or looseness in the sterndrive when steering, unusual noises during turning, or visible corrosion and wear on the pins themselves during inspection. A loose feeling at the helm can often be traced back to worn hinge pins.
How does this aftermarket tool compare to the OEM version?
This tool is manufactured from high-strength hardened steel to meet or exceed OEM specifications for strength and durability. It provides the same functionality and fit as the original manufacturer's tool at a more accessible price point.
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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