Mercury Carburetor Float Bowl O-Ring 25-16259
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Mercury Carburetor Float Bowl O-Ring 25-16259
Part Number: 25-16259 (short ref: 16259)
Brand: Mercury / Quicksilver
Product Type: Carburetor Float Bowl O-Ring (OEM)
System: Outboard Fuel System / Carburetor
Position: Between carburetor body and float bowl
Quantity Required: 1 per carburetor
GTIN / UPC: 745061117433
Approximate Weight: 5 g
What This Part Does
The 25-16259 is a genuine OEM O-ring that seals the float bowl to the carburetor body on selected small Mercury and Mariner 2-stroke outboards. It prevents fuel from leaking at the bowl joint during operation. The seal is replaced whenever the float bowl is removed for service — reusing a compressed or aged O-ring risks a fuel leak after reassembly.
Compatible Applications
Confirm your engine horsepower, serial number, carburetor model, and float-bowl diagram before ordering. Mercury used several different carburetor assemblies across these horsepower ranges — do not select by O-ring diameter or appearance alone.
- Mercury / Mariner 4 HP 2-stroke
- Mercury / Mariner 5 HP 2-stroke
- Mercury / Mariner 6 HP 2-stroke
- Mercury / Mariner 8 HP 2-stroke
- Mercury / Mariner 9.8 HP 2-stroke
- Mercury / Mariner 9.9 HP 2-stroke
- Selected SeaPro and international variants in these horsepower ranges
Serial Number Notice
Mercury used several different carburetor and float-bowl seal designs across otherwise similar 4–9.9 HP engines. Nearby fuel-system seals in the same carburetor assembly can look identical but carry different part numbers. Always match by part number and confirm against the float-bowl diagram for your specific engine serial number.
When to Replace
- Float bowl is removed for any reason during carburetor service (replace as standard practice)
- Fuel leakage visible around the float-bowl joint
- O-ring is flattened, permanently compressed, or no longer sealing
- Rubber has hardened, cracked, or become brittle
- Seal is cut, swollen, or distorted on inspection
- Carburetor cleaning reveals deterioration of the existing seal
Installation Notes
- Clean the float-bowl sealing groove and mating surface before installing the new O-ring
- Seat the O-ring evenly without twisting, stretching, or pinching
- On later applications, 25-16259 installs with float bowl 803691T01, four float-bowl screws 162601, and drain-screw gasket 16262 — inspect all of these during carburetor service
- Do not reuse the old O-ring after bowl removal
- Check for fuel leaks at the bowl joint after reassembly and before returning the engine to service
Part Number Cross-Reference
- Current OEM: 25-16259
- Short Reference: 16259
Parts Desk Insights
Best use case: Order 25-16259 any time the float bowl is coming off a 4–9.9 HP Mercury or Mariner 2-stroke carburetor — replacing the O-ring at the same time as any carburetor cleaning or rebuild is the right call since access is already there and the part is low cost.
Common issues: The most frequent mistake is selecting by physical size or appearance rather than part number — several seals in the same carburetor assembly look similar but are not interchangeable. A second common issue is reusing the old O-ring after disassembly — a compressed or aged seal that appeared acceptable on the bench often leaks once the bowl is back under fuel pressure and heat cycles.
Related Parts
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
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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.
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Important:
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