Stainless Steel Skeg Guard for Mercury MerCruiser Alpha One 1985-1990
This marine-grade stainless steel skeg guard is designed to protect the outdrives on Mercury MerCruiser Alpha One Gen 1 models manufactured between 1985 and 1990. It serves as a reliable solution for covering a damaged or broken skeg, preventing further damage while restoring performance and appearance.
This aftermarket component directly replaces MerCruiser 27021, GlückMarine 27021, sevencow 27021-TP1, and VT-MOTOR 27021.
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Installation Method: Simple bolt-on design requires no welding.
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Material Construction: Made from durable, mirror-polished 316 stainless steel for superior corrosion resistance.
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Protective Design: Includes a drain hole to prevent water from collecting and causing corrosion or damage from freezing.
Part Number Cross-Reference
Use this table to confirm equivalent part numbers across OEM and aftermarket brands.
| Brand |
Part Number |
| MerCruiser |
27021 |
| GlückMarine |
27021 |
| sevencow |
27021-TP1 |
| VT-MOTOR |
27021 |
Compatible Engine Models
Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.
| Brand |
Model |
Rated HP |
Years |
OEM Part No. |
Notes |
| MerCruiser |
Alpha One Gen 1 |
All |
1985-1990 |
27021 |
Sterndrive application |
| Mercury |
Alpha 1 |
All |
1985-1990 |
27021 |
Sterndrive application |
Technical Specifications
| Specification |
Value |
| Product Type |
Skeg Guard/Protector |
| Installation |
Bolt-On |
| Material |
Marine-Grade 316 Stainless Steel |
| Finish |
Mirror-Polished |
| Thickness |
1.6 mm (1/16") |
| Weight |
0.5 kg (1.1 lbs) |
| Design Features |
Drain hole to prevent corrosion and water freezing |
| Application |
For protection or repair of damaged skegs |
| Minimum Skeg Remaining |
50-76 mm (2-3") |
| Installation Time |
Approximately 10 minutes |
| Warranty |
1 Year |
Package Contents
- 1 x Skeg Guard (27021)
- 2 x Hex Wrench
- 2 x Female Locking Screws
- 2 x Big Male Locking Screws
- 2 x Small Male Locking Screws
- 1 x Loctite 262 (if purchased from certain retailers)
Installation Guide
- Clean the exterior of your existing skeg, removing any marine growth or debris. Ensure the engine is off and the drive is tilted up for safe access.
- Confirm you have at least 2-3 inches (50-76 mm) of your original skeg remaining for the guard to properly mount.
- Slide the skeg guard over the damaged skeg to test the fit. The guard should fit snugly.
- Insert the female locking screws into the skeg guard.
- Apply the included Loctite threadlocker to the male mounting screws to prevent them from loosening due to vibration.
- Align the mounting holes and insert the appropriate male locking screws. Tighten them evenly using the provided hex wrenches until the guard is securely fastened. Do not overtighten.
- Check for any gaps or movement. Once secure, the installation is complete.
Troubleshooting & FAQ
Q: How do I confirm this fits my engine?
A: This skeg guard is designed specifically for Mercury and MerCruiser Alpha One Gen 1 sterndrives from 1985-1990. Please verify your drive model and year by checking the compatibility table above. It replaces OEM part number 27021.
Q: How much of my original skeg needs to be left for this guard to install correctly?
A: You must have a minimum of 2 to 3 inches (50-76 mm) of the original skeg remaining. This is required to provide a solid mounting base for the bolt-on installation.
Q: What is the purpose of the drain hole at the bottom?
A: The drain hole is a key design feature that prevents water from collecting inside the guard. This helps prevent corrosion, galvanic action, and potential damage from water freezing and expanding in colder climates.
Q: Is drilling or welding required for installation?
A: No. This is a bolt-on part that does not require any drilling or welding. The kit includes all necessary mounting hardware and can be installed in approximately 10 minutes.
Q: OEM vs. Aftermarket?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.
Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.
Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.
Important Notes
- Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
- This product is an aftermarket replacement part and is not an OEM component.
- Professional installation is recommended to ensure safety and optimal performance.
Why Choose JLM MARINE?
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Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
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Fast Global Shipping: Free delivery worldwide in 5–15 days.
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Direct from Manufacturer: Competitive pricing without compromising quality.