Main Bearing (2) – Fits Yanmar 3GM30 Series Marine Diesel Engines (Replaces 121450-02170)
Main Bearing (2) – Fits Yanmar 3GM30 Series Marine Diesel Engines (Replaces 121450-02170) is backordered and will ship as soon as it is back in stock.
Couldn't load pickup availability
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
Main Bearing (2) – Fits Yanmar 3GM30 Series Marine Diesel Engines (...
Product Details
This is a replacement Main Bearing (2) designed for Yanmar 3GM30 series marine diesel engines, including 3GM30, 3GM30F, and 3GM30VE models manufactured between 1983 and 2005. It serves as the critical central (middle) bearing for the crankshaft, ensuring smooth engine operation.
It is a direct replacement for Yanmar OEM part number 121450-02170.
- Installs in the engine block's main bearing housing.
- Engineered as the middle/central main bearing for the 3GM30 series.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yanmar | 121450-02170 | Main bearing (2) / Central |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This part is specifically for the Yanmar models listed. Ensure your engine is a 3GM30 series before purchasing.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yanmar | 3GM30 | 24 | 3-Cylinder | 1983–2005 | 121450-02170 | Main bearing (2) / Central |
| Yanmar | 3GM30VE | 24 | 3-Cylinder | 1983–2005 | 121450-02170 | Main bearing (2) / Central |
| Yanmar | 3GM30F | 27 | 3-Cylinder | 1983–2005 | 121450-02170 | Main bearing (2) / Central |
| Yanmar | 3GM30F-YEU | 27 | 3-Cylinder | 1983–2005 | 121450-02170 | Main bearing (2) / Central |
| Yanmar | 3GM30-YEU | 24 | 3-Cylinder | 1983–2005 | 121450-02170 | Main bearing (2) / Central |
| Yanmar | 3GM30B | 24 | 3-Cylinder | 1983–2005 | 121450-02170 | Main bearing (2) / Central |
| Yanmar | 3GM30C | 24 | 3-Cylinder | 1983–2005 | 121450-02170 | Main bearing (2) / Central |
Technical Specs
- Product Type
- Main Bearing (Central)
- Installation
- Engine Block Main Bearing Housing
- Dimensions
- Height: 7.0; Width: 4.0; Length: 7.0;
- Other Technical Attributes
- Middle/central main bearing for 3GM30 series engines
What’s in the Box
- 1 x Main Bearing (121450-02170)
Installation Notes
- Disconnect the negative battery terminal and safely drain the engine oil.
- Access the engine's lower end by carefully removing the oil pan and gasket.
- Identify the central main bearing cap, then unbolt and remove it.
- Carefully remove the old upper and lower bearing shells from the engine block and cap.
- Thoroughly clean the bearing housing surfaces and crankshaft journal to remove all oil and debris.
- Apply a quality engine assembly lubricant to the surface of the new bearing shells.
- Install the new bearing shells, ensuring they are correctly seated in the block and cap.
- Reinstall the main bearing cap and torque the bolts to the manufacturer's specified sequence and values.
- Verify the crankshaft rotates freely without binding before proceeding.
- Reinstall the oil pan with a new gasket and refill the engine with the correct grade of oil.
Troubleshooting & FAQ
How do I know if this is the correct main bearing for my engine?
This is the central (No. 2) main bearing. Verify your engine is a Yanmar 3GM30 series model listed in the compatibility table. Always compare the part number 121450-02170 with your service manual's requirements for the specific bearing position.
What are the signs of a failing main bearing?
Common symptoms include a deep, knocking sound from the engine's bottom end (rod knock), low or fluctuating oil pressure readings, and the presence of metallic particles (bearing material) in the engine oil and filter.
Can I replace just one main bearing?
While possible in an emergency, it is strongly recommended to inspect and replace all main bearings as a complete set during an engine rebuild. This ensures even wear, consistent oil clearances, and long-term engine reliability.
What is the difference between this bearing and other main bearings in the 3GM30 engine?
The Yanmar 3GM30 series uses bearings of different specifications for different journal positions. This part, 121450-02170, is specifically the central or "middle" bearing, designated as "main metal (2)" in the official Yanmar parts catalog.
Is any special preparation needed before installation?
Yes. Absolute cleanliness is crucial. Ensure the crankshaft journal and engine block housing are perfectly clean and free of old oil, dirt, or debris. Apply a liberal amount of quality engine assembly lubricant to the bearing faces before installation. Do not use regular motor oil for initial assembly.
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
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
