Seachoice 50-21121 In-Line Fuel Filter – 3/8 in. | 20 Micron | Johnson/Evinrude
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Seachoice 50-21121 – In-Line Fuel Filter | 3/8 in. Barb | 20 Micron
Part Number: 50-21121 | Reference: 21121
Brand: Seachoice
Type: In-Line Outboard Fuel Filter
Filtration: 20 Micron
Barb Size: 3/8 in.
Construction: Molded White Plastic
UPC: 719249211213
A clean fuel supply is essential for reliable outboard performance. The Seachoice 50-21121 installs directly in the fuel line and filters contaminants to 20 microns before they reach carburetors or other downstream fuel-system components. Molded white plastic body for easy visual inspection.
Compatible Applications
- Johnson/Evinrude outboard engines using 3/8 in. in-line fuel filter configuration
- Cross-references to Johnson/Evinrude 398319 and 398318
Fitment Notice: Confirm your existing fuel filter part number and fuel-line hose diameter before ordering. Seachoice offers the same 20-micron filter in 1/4 in. and 5/16 in. barb sizes — matching the hose size is critical for a leak-free installation.
When to Replace
Replace the fuel filter during routine fuel-system maintenance, or if you notice any of the following:
- Hard starting or rough running caused by restricted fuel flow
- Visible contamination or discoloration inside the filter body
- Cracking, leaking, or deterioration of the filter housing
Installation Notes
- Use properly sized 3/8 in. marine-rated fuel hose and appropriate clamps
- Install with the fuel-flow arrow pointing toward the engine
- Ensure both barb connections are fully seated and clamps are tight
- Inspect carefully for leaks before operating the engine
Cross-Reference Part Numbers
- Seachoice: 50-21121 / 21121
- Johnson/Evinrude: 398319
- Johnson/Evinrude (also replaces): 398318
- UPC: 719249211213
Related Filters in This Series
- Seachoice 50-21101 – In-Line Fuel Filter, 1/4 in. | 20 Micron
- Seachoice 50-21111 – In-Line Fuel Filter, 5/16 in. | 20 Micron
Parts Desk Insights
The quickest way to identify which filter you need from the Seachoice 20-micron series is the barb size: this 50-21121 uses 3/8 in. connections, the 50-21101 uses 1/4 in., and the 50-21111 uses 5/16 in. The most common mistake is ordering based on engine model alone without checking hose diameter — measure your existing fuel line before purchasing. This filter is a straightforward maintenance item and a good replacement candidate any time a fuel-related issue is being diagnosed.
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.