Engine Coupler – Fits Volvo Penta/OMC 4.3L/5.0L/5.7L (Replaces 3858437, 3858437-1)
Engine Coupler – Fits Volvo Penta/OMC 4.3L/5.0L/5.7L (Replaces 3858437, 3858437-1) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Product Details
This replacement Engine Coupler – Fits Volvo Penta/OMC 4.3L/5.0L/5.7L is engineered for a precise fit on specific GM engines manufactured between 1986 and 1998. It is designed for V6 and V8 models that utilize a 17-spline drive shaft and a one-piece rear main seal, ensuring reliable power transmission from the engine to the sterndrive.
It serves as a direct interchange for Sierra 18-21752-1, OMC part numbers 3853917, 3858437, 984290, and 986120, and Volvo Penta part numbers 3858437, 3858437-1, 985727, and 3853862-5.
- Features a robust 17-spline design for secure engagement.
- Engineered for direct-bolt replacement to simplify installation.
- Specifically compatible with post-1986 GM engines using a one-piece rear main seal.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Sierra | 18-21752-1 |
| OMC | 3853917 |
| OMC | 3858437 |
| OMC | 984290 |
| OMC | 986120 |
| Volvo Penta | 3858437 |
| Volvo Penta | 3858437-1 |
| Volvo Penta | 985727 |
| Volvo Penta | 3853862-5 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Volvo Penta applications, this coupler fits various Gi, GL, GS, and GXi series engines, as well as several numbered series from 1989–1993.
| Brand | Model | Rated HP | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Volvo Penta | 4.3Gi/GL/GS/GXi Series | 160-225 | 1986–1998 | 3858437, 3858437-1 | Multiple HP ratings across series |
| Volvo Penta | 5.0Gi/GL/GS/GXi Series | 190-270 | 1986–1998 | 3858437, 3858437-1 | Multiple HP ratings across series |
| Volvo Penta | 5.7Gi/GL/GS/GXi Series | 215-320 | 1986–1998 | 3858437, 3858437-1 | Multiple HP ratings across series |
| Volvo Penta | 430A/430B/431A/431B/432A/434A | 205 | 1989–1993 | 3858437, 3858437-1 | Various engine designations |
For OMC applications, the coupler is compatible with a wide range of Cobra and SX sterndrive models paired with GM V6 and V8 engines.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| OMC | 4.3L (262 CID) Cobra/SX | 1986–1998 | 3853917, 3858437, 984290, 986120 | Various engine designations |
| OMC | 5.0L (305 CID) Cobra/SX | 1986–1998 | 3853917, 3858437, 984290, 986120 | Various engine designations |
| OMC | 5.7L (350 CID) Cobra/SX | 1986–1998 | 3853917, 3858437, 984290, 986120 | Various engine designations |
Technical Specs
- Product Type
- Engine Coupler
- Installation
- Direct-bolt replacement
- Spline Count
- 17
- Compatible Engines
- GM 4.3L (262 CID), 5.0L (305 CID), 5.7L (350 CID)
- Rear Main Seal Type
- One-piece design (post-1986 engines)
- Material
- Metal (specific alloy not specified)
- Product Dimensions
- Height: 16.5; Width: 16.5; Length: 20.0
What’s in the Box
- 1 x Engine Coupler Assembly
Installation Notes
- Disconnect the battery and ensure the engine is cool.
- Remove the sterndrive assembly to access the engine coupler.
- Unbolt and remove the old coupler from the engine flywheel.
- Clean the flywheel surface and inspect it for damage.
- Align the new coupler with the flywheel and driveshaft splines.
- Install and torque the mounting bolts to the manufacturer's specifications.
- Reinstall the sterndrive, ensuring proper alignment.
- Reconnect the battery and test the engine and drive operation in a safe environment.
Troubleshooting & FAQ
How do I know if my engine coupler is failing?
Common signs of a failing engine coupler include excessive vibration, especially at idle or when shifting into gear, unusual rattling or clunking noises from the engine/drive area, and visible damage or cracks upon inspection.
How can I confirm this is the right part for my engine?
This coupler is specifically for 1986–1998 GM engines (4.3L, 5.0L, 5.7L) with a one-piece rear main seal and a 17-spline driveshaft. Please verify your spline count and rear main seal type before ordering. It is not compatible with Ford engines.
What are the signs of a bad engine alignment?
Poor engine alignment is a primary cause of premature coupler failure. If you experience persistent vibration even with a new coupler, your engine alignment should be checked by a qualified marine technician using the proper alignment tools.
Is this coupler compatible with engines made before 1986?
No. This part is designed for engines manufactured from 1986 onwards, which use a one-piece rear main seal. Earlier models typically use a two-piece seal and require a different coupler.
What's the difference between this coupler and one for a Ford engine?
The primary differences are the bolt pattern and spline count. This GM-specific coupler has a 17-spline design, whereas couplers for Ford engines may have a different configuration. They are not interchangeable.
Can I install this part myself?
While installation is possible for those with advanced mechanical skills and the correct tools (including an engine alignment tool), we recommend professional installation to ensure proper alignment and prevent premature failure or damage to other components.
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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