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11-859135 Lower Gear Casing Mounting Nut for MerCruiser Alpha One Gen II | JLM Marine
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Lower Gear Casing Mounting Nut – Fits MerCruiser Alpha One Gen II
This lower gear casing mounting nut is engineered to fit MerCruiser Alpha One Gen II stern drives. Designed as a direct replacement for part number 11-859135, it ensures secure mounting and reliable performance in demanding marine environments.
This aftermarket component directly replaces OEM part numbers 11-817618 and 11-859135 (also listed as 859135), providing a cost-effective solution without compromising quality or fitment.
- Precision-engineered for Alpha One Gen II applications
- Direct fit for lower gear casing assembly (see diagram part 76)
- Durable construction for long-term marine use
Part Number Cross-Reference
Use this table to confirm equivalent part numbers across OEM and aftermarket brands.
| Brand | Part Number | Notes |
|---|---|---|
| MerCruiser | 11-859135 | Primary OEM reference |
| MerCruiser | 859135 | Alternate listing |
| MerCruiser | 11-817618 | Superseded by 11-859135 |
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 | Notes |
|---|---|---|
| MerCruiser | Alpha One Gen II | Lower gear casing mounting nut (Part 76 in exploded diagram) |
Technical Specifications
| Specification | Value |
|---|---|
| OEM Part Number | 11-859135 |
| Application | Lower gear casing mounting |
| Fitment | MerCruiser Alpha One Gen II stern drives |
| Diagram Reference | Part 76 |
Package Contents
- 1 × Lower Gear Casing Mounting Nut (OEM# 11-859135)
Installation Guide
- Ensure the stern drive is properly supported and the lower unit is removed according to manufacturer service manual procedures.
- Clean the mounting threads on the gear casing and inspect for damage or corrosion.
- Position the lower gear casing alignment components as specified in your service manual.
- Thread the mounting nut onto the gear casing by hand to prevent cross-threading.
- Torque the nut to the manufacturer's specification using a calibrated torque wrench (refer to your Alpha One Gen II service manual for exact values).
- Verify all alignment and clearances before reassembling the drive unit.
- Reinstall the lower unit following MerCruiser service procedures and perform a functional test.
Troubleshooting & FAQ
Q: How do I confirm this nut fits my MerCruiser drive?
A: Verify your stern drive is an Alpha One Gen II model. Cross-reference part number 11-859135 or 11-817618 in your service manual or exploded parts diagram (Part 76). If your original nut matches these specifications, this replacement will fit.
Q: What torque specification should I use when installing this nut?
A: Always follow the torque values specified in your MerCruiser Alpha One Gen II service manual. Over-tightening can damage threads or the gear casing; under-tightening may cause improper alignment or loosening during operation.
Q: When should I replace the lower gear casing mounting nut?
A: Replace this nut if you notice thread damage, corrosion, deformation, or if it cannot achieve proper torque specification. It should also be inspected during any lower unit service or gear casing work.
Q: What's the difference between this aftermarket nut and the OEM part?
A: This aftermarket replacement is manufactured to OEM specifications using comparable-grade materials. It provides the same fitment and function as the original MerCruiser part at a more competitive price point.
Q: Is this part OEM or 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?
- Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
- Fast Global Shipping: Free delivery worldwide in 5–15 days.
- Direct from Manufacturer: Competitive pricing without compromising quality.
We can ship to virtually any address in the world with free shipping available for most regions.
For our typical US and Canadian customers , our shipping timeframes are as follows:
- Amazon FBA: orders will be delivered within 1-5 business days after placing the order (during certain special periods such as major promotions, Christmas, etc., the delivery time of Amazon FBA may be affected).
- US warehouse shipment: orders will be delivered within 5 days after placing the order.
- China warehouse shipment: orders will be delivered about 12 days after placing the order.
When you place an order, we will estimate shipping and delivery dates for you based on the availability of your items and the shipping options you choose. Depending on the shipping provider you choose, shipping date estimates may appear on the shipping quotes page.
Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can be found on its detail page. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.
Founded in 2002, JLM Marine has established itself as a dedicated manufacturer of high-quality marine parts, based in China. Our commitment to excellence in manufacturing has earned us the trust of top marine brands globally.
As a direct supplier, we bypass intermediaries, which allows us to offer competitive prices without compromising on quality. This approach not only supports cost-efficiency but also ensures that our customers receive the best value directly from the source.
We are excited to expand our reach through retail channels, bringing our expertise and commitment to quality directly to boat owners and enthusiasts worldwide.
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