Seachoice 50-21021 Full-Flow Oil Filter – 20 Micron | Yanmar & Westerbeke Marine Diesel
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Seachoice 50-21021 Full-Flow Oil Filter – 20 Micron
Part Number: 50-21021 | SKU: 50-21021 | UPC: 719249210216
The Seachoice 50-21021 is a 20-micron full-flow spin-on oil filter for compatible Yanmar and Westerbeke marine diesel engines. It crosses directly to Sierra 18-7910-1, Westerbeke 30220, and multiple Yanmar OEM filter numbers. Built with high-efficiency cellulose filter media, an epoxy-coated corrosion-resistant canister, reinforced body construction, heavy-duty end-cap seals, and an anti-drain-back valve, it meets or exceeds original equipment filtration requirements for applicable Yanmar and Westerbeke diesel applications.
Key Specifications
- Filtration: 20 micron
- Filter type: Full-flow spin-on
- Thread: 20 mm x 1.5
- Filter media: High-efficiency cellulose
- Anti-drain-back valve: Yes
- Canister: Epoxy-coated steel for corrosion resistance
- Body: Reinforced construction
- End-cap seals: Heavy-duty
- Manufactured in an ISO/TS 16949 certified facility
Compatible Applications
- Yanmar 1GM marine diesel engines
- Yanmar 1GM10 marine diesel engines
- Yanmar 2GM marine diesel engines
- Yanmar 2GMF marine diesel engines
- Yanmar 2GM20 marine diesel engines
- Yanmar 2GM20F marine diesel engines
- Yanmar 3GM marine diesel engines
- Yanmar 3GMF marine diesel engines
- Yanmar 3GM30 marine diesel engines
- Yanmar 3GM30F marine diesel engines
- Westerbeke marine diesel engines specifying Westerbeke 30220 or Sierra 18-7910-1
Fitment Note: Confirm your engine model and existing filter part number before ordering. The 20 mm x 1.5 thread and cross-reference to Yanmar 124450-35100 or Westerbeke 30220 are the most reliable fitment identifiers. Match by part number rather than appearance alone.
Service Interval
Replace at every scheduled engine oil service. Marine diesel engines typically require more frequent oil and filter changes than gasoline engines — follow the engine manufacturer’s recommended service interval for your specific Yanmar or Westerbeke model. Refer to your engine service manual for guidance.
Installation Notes
- Remove the old filter and confirm the old gasket has come away with it — a retained gasket will cause an oil leak
- Clean the filter mounting surface
- Lightly coat the new filter gasket with fresh engine oil before threading it on
- Tighten by hand plus ¾ turn, or per engine manufacturer specification — do not over-tighten
- Run the engine and inspect for leaks before returning to service
Cross-Reference Part Numbers
- Seachoice: 50-21021 / 21021
- Sierra: 18-7910-1
- Westerbeke: 30220
- Yanmar: 124450-35100, 119350-35150, 119350-35151, 119660-35150
- Mallory: 9-57810
Related Products
- Sierra 47-237800 Oil Filter – Westerbeke Marine Diesel Engine — Sierra diesel filter for Westerbeke applications
- Sierra 18-7884 Diesel Oil Filter – Universal & Volvo Penta Marine Diesel — alternate marine diesel oil filter
- Sierra 79101 Diesel Oil Filter — alternate Sierra marine diesel filter
- Sierra Oil Drain Kit – 1/2"-20 Thread, 42" Length (47-7891)
Parts Desk Insights
Best Use Case: Routine oil and filter changes on Yanmar 1GM, 2GM, and 3GM-series marine diesel engines — some of the most common compact diesel auxiliaries found on sailboats and small trawlers — as well as compatible Westerbeke diesel applications. Diesel engine oil services tend to come around more frequently than gasoline equivalents, making this a high-turnover maintenance item for shops serving sailboat and trawler owners.
Common Issues: Yanmar uses multiple filter part numbers across their GM-series engine families, and several filters look similar. The safest confirmation is matching Yanmar 124450-35100 or Sierra 18-7910-1 against the engine’s service records or existing filter. The 20 mm x 1.5 thread is also a useful cross-check. Always remind customers to verify the old gasket came off with the old filter before installing the new one — a double gasket on the mount is a common source of post-service oil leaks on these small diesels.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.