Mercury MerCruiser Quicksilver Gearcase O-Ring 457101
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Gearcase O-Ring — OEM Reference 457101 / 25-457101
Part Number: 457101 | Service format: 25-457101
Brand: Mercury Marine / Quicksilver
Official Product Type: Gearcase O-Ring — Shift-Shaft / Bushing Seal
Supersedes: 457101 / 25-457101
Replaced By: 8M0204681 / 25-8M0204681
Size: 1.424” ID × 0.103” cross-section (orange)
System: Lower Unit — Gearcase Sealing
Diagram Position: Shift-shaft / bushing area of compatible gear housings
GTIN: 745061532595
What This O-Ring Does
This genuine Mercury Marine / Quicksilver O-ring seals the shift-shaft and bushing area in compatible Mercury and Mariner lower-unit gear housings. The 1.424” inside diameter and 0.103” cross-section are specific to this application — a generic O-ring of similar outer size may have the wrong cross-section or material, which changes how it compresses in the housing and increases the risk of lubricant loss or water intrusion into the gearcase.
Compatible Applications
Fitment depends on exact engine model, serial number, and gearcase diagram. Confirm against your Mercury parts diagram before ordering.
- Mercury / Mariner 30–125 HP 2-stroke lower-unit assemblies
- Mercury / Mariner 50–150 HP 4-stroke lower-unit assemblies
- Selected Mercury / Mariner 115 HP EFI FourStroke gear housings
- Mercury / Mariner 40–115 HP EFI and 75/90/115 HP DFI / Optimax gearcases (serial-number dependent)
- MerCruiser Bravo drive shaft housing and related gearcase component groups (confirm by diagram)
- Other lower-unit assemblies using the same shift-shaft / bushing seal arrangement
Serial Number Fitment Notice
Mercury uses several similar O-rings in the same gearcase and shift-shaft assembly area. Matching by part number (457101 / 8M0204681) and confirming the diagram callout by serial number is more reliable than selecting by appearance or size alone.
When to Replace This O-Ring
Replace whenever the surrounding gearcase or shift-shaft components are removed for service, or if the existing O-ring is flattened, hardened, cut, swollen, or showing signs of lubricant leakage or water intrusion.
Service Interval
Replace at every gearcase or shift-shaft service. Reusing a disturbed O-ring is not recommended — the cost of a new seal is negligible compared to a repeat service call caused by a failed O-ring.
Dimensions
Inside diameter: 1.424 in. | Cross-section: 0.103 in. | Color: Orange (current OEM replacement reference)
Installation Notes
- Clean the O-ring groove and mating surfaces before installation.
- Inspect the adjacent shift-shaft bushing, oil seal, and retaining components while the gearcase is apart.
- Install the new O-ring without twisting or nicking it.
- Lubricate according to the applicable Mercury service procedure before seating.
Kit Contents
Single O-ring. Not a kit. Order related gearcase seals and O-rings separately for a complete lower-unit service.
Alternate and Superseded Part Numbers
- Original: 457101 / 25-457101
- Related: 45710 / 25-45710
- Current OEM replacement: 8M0204681 / 25-8M0204681
- Aftermarket cross-reference: Sierra 18-7198, GLM 81270 / 81275
- Related interchange: OMC / Johnson / Evinrude 0308626, 0508504, 0777523; Honda 91353-ZW1-003
Related Parts
- Gearcase shift-shaft bushing — verify by engine model and serial number
- Gearcase oil seal set — verify by engine model and serial number
- Lower-unit gear lube — required when servicing the gearcase
Parts Desk Insights
This O-ring is most often ordered during a gearcase or shift-shaft service on assemblies that specifically call for 457101. The detail customers miss is that a similar-looking O-ring with the same outer diameter but a different cross-section won’t compress the same way in the housing groove — which can lead to a slow gear-lube leak or water getting into the lower unit. Order the current replacement 8M0204681 if original 457101 stock is unavailable; they serve the same function.
Technical FAQ
Q: Can I use any O-ring with the same outer diameter?
No. The cross-section (0.103”) is as important as the diameter. An incorrect cross-section changes how the O-ring seats and seals in the groove.
Q: Is 8M0204681 the same O-ring as 457101?
Yes — 8M0204681 is the current OEM replacement for 457101. It may appear different (often orange vs. black) while performing the same sealing function.
Q: How do I confirm this is the right O-ring for my engine?
Use your Mercury or Mariner engine serial number to look up the gearcase diagram and confirm the callout specifically lists 457101 or 8M0204681 at the shift-shaft / bushing location.
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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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.
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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:
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