Mercury Quicksilver — MerCruiser Fuel System O-Ring — 805970
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Mercury Quicksilver 805970 Fuel System O-Ring
Maintain the seal at compatible MerCruiser fuel-system connections with this genuine Mercury Marine replacement O-ring, also catalogued as 25-805970. The serial-specific fuel cooler or vapor separator tank (VST) and fuel rail diagram determines the correct location and quantity.
Compatible Applications
- MerCruiser 350 MAG EFI, 5.7L EFI, Black Scorpion 350 MAG, and MX 6.2L engines
- MerCruiser 454/7.4L EFI and MPI engines
- MerCruiser 502/8.2L EFI and MPI engines
- Example applications include 454 MAG MPI Bravo Gen VI, serial 0F802350–0K999999, and 502 MAG MPI Gen VI, serial 0F802600–0K999999. Confirm the installed fuel-system layout by engine serial number.
Part Details
- Brand: Mercury Quicksilver
- Part number: 805970, catalogued as 25-805970
- Product type: Fuel system O-ring
- Sold individually
- Quantity depends on the diagram: some VST and fuel rail layouts call for two; the cited fuel cooler layout calls for one
- Neighbouring O-rings 805531 and 805407 are different parts
- No superseding Mercury number is listed in the referenced diagrams
When to Replace
Replace an O-ring that is cut, flattened, swollen, or damaged when a fuel connection is disconnected. Inspect the connection for leaks after reassembly.
Installation Notes
Keep the seal and mating surfaces clean, avoid twisting or pinching the O-ring, and follow the MerCruiser fuel-system service procedure. Do not substitute a similar-looking O-ring unless its size and material are confirmed for the application.
Technical FAQ
How many O-rings should I order? Check the correct serial-specific diagram. Some VST and fuel rail layouts call for two, while the cited fuel cooler layout calls for one.
Can I substitute a nearby O-ring? No. Confirm part number 805970 and the diagram position; 805531 and 805407 are different parts.
Parts Desk Insights
Best use: Replacing the seal at a compatible fuel cooler, VST, or fuel rail connection.
Common mistake to avoid: Choosing a similar-looking nearby seal or assuming every assembly uses the same quantity.
Sizing and fitment: Physical dimensions and material are not specified here. Match the engine serial number to the correct fuel-system diagram and confirm the listed part number and quantity before ordering.
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.